sec.man

.\"
.\" SEC (Simple Event Correlator) 2.9.3 - sec.man
.\" Copyright (C) 2000-2024 Risto Vaarandi
.\"
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.\" 
.TH sec 1 "November 2024" "SEC 2.9.3"
.SH NAME
sec \- simple event correlator
.SH SYNOPSIS
.TP 
.B sec
[--conf=<file pattern> ...]
.br
[--input=<file pattern>[=<context>] ...]
.br
[--input-timeout=<input timeout>]
.br
[--timeout-script=<timeout script>]
.br
[--reopen-timeout=<reopen timeout>]
.br
[--check-timeout=<check timeout>]
.br
[--poll-timeout=<poll timeout>]
.br
[--socket-timeout=<socket timeout>]
.br
[--blocksize=<io block size>]
.br
[--bufsize=<input buffer size>]
.br
[--evstoresize=<event store size>]
.br
[--cleantime=<clean time>]
.br
[--log=<logfile>]
.br
[--syslog=<facility>]
.br
[--debug=<debuglevel>]
.br
[--pid=<pidfile>]
.br
[--dump=<dumpfile>]
.br
[--user=<username>]
.br
[--group=<groupname> ...]
.br
[--umask=<mode>]
.br
[--ruleperf | --noruleperf]
.br
[--dumpfts | --nodumpfts]
.br
[--dumpfjson | --nodumpfjson]
.br
[--quoting | --noquoting]
.br
[--tail | --notail]
.br
[--fromstart | --nofromstart]
.br
[--detach | --nodetach]
.br
[--jointbuf | --nojointbuf]
.br
[--keepopen | --nokeepopen]
.br
[--rwfifo | --norwfifo]
.br
[--childterm | --nochildterm]
.br
[--intevents | --nointevents]
.br
[--intcontexts | --nointcontexts]
.br
[--testonly | --notestonly]
.br
[--help] [-?]
.br
[--version]
.SH DESCRIPTION
SEC is an event correlation tool for advanced event processing which can
be harnessed for event log monitoring, for network and security management, 
for fraud detection, and for any other task which involves event correlation.
Event correlation is a procedure where a stream of events is processed, 
in order to detect (and act on) certain event groups that occur within 
predefined time windows. Unlike many other event correlation products which
are heavyweight solutions, SEC is a lightweight and platform-independent
event correlator which runs as a single process. The user can start it as
a daemon, employ it in shell pipelines, execute it interactively in
a terminal, run many SEC processes simultaneously for different tasks, 
and use it in a wide variety of other ways.
.PP
SEC reads lines from files, named pipes, or standard input,
matches the lines with patterns (regular expressions, Perl subroutines, etc.) 
for recognizing input events, and 
correlates events according to the rules in its configuration file(s). 
Rules are matched against input in the order they are given in 
the configuration file.
If there are two or more configuration files, rule sequence from every file
is matched against input (unless explicitly specified otherwise).
SEC can produce output by executing external programs (e.g., 
.BR snmptrap (1)
or
.BR mail (1)), 
by writing to files, by sending data to TCP and UDP based servers, 
by calling precompiled Perl subroutines, etc. 
.PP
SEC can be run in various ways. For example, the following command line
starts it as a daemon, in order to monitor events appended to the 
/var/log/messages syslog file with rules from /etc/sec/syslog.rules:
.PP
/usr/bin/sec --detach --conf=/etc/sec/syslog.rules \\
             --input=/var/log/messages
.PP
Each time /var/log/messages is rotated, a new instance of /var/log/messages
is opened and processed from the beginning. The following command line
runs SEC in a shell pipeline, configuring it to process lines from standard
input, and to exit when the /usr/bin/nc tool closes its standard output 
and exits:
.PP
/usr/bin/nc -l 8080 | /usr/bin/sec --notail --input=- \\
                                   --conf=/etc/sec/my.conf
.PP
Some SEC rules start event correlation operations, while other rules react
immediately to input events or system clock. For example, suppose that SEC
has been started with the following command line
.PP
/usr/bin/sec --conf=/etc/sec/sshd.rules --input=/var/log/secure
.PP
in order to monitor the /var/log/secure syslog file for sshd events. 
Also, suppose that the /etc/sec/sshd.rules configuration file contains
the following rule for correlating SSH failed login syslog events:
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from [\\d.]+ port \\d+ ssh2
.br
desc=Three SSH login failures within 1m for user $1
.br
action=pipe '%s' /bin/mail -s 'SSH login alert' root@localhost
.br
window=60
.br
thresh=3
.PP
The 
.I pattern
field of the rule defines the pattern for recognizing input events, while the
.I ptype
field defines its type (regular expression). Suppose that user risto fails to 
log in over SSH and the following message is logged to /var/log/secure:
.PP
Dec 16 16:24:59 myserver sshd[13685]: Failed password for risto from 10.12.2.5 port 41063 ssh2
.PP
This input message will match the regular expression
pattern of the above rule, and the match variable $1 will be set to the string
.I risto 
(see
.BR perlre (1)
for details).
After a match, SEC will evaluate the operation description string given with 
the
.I desc
field. This is done by substituting $1 with its current value which yields 
.IR "Three SSH login failures within 1m for user risto" .
SEC will then check if there already exists an event correlation operation
identified with this string and triggered by the same rule. 
If the operation is not found, SEC will create 
a new operation for the user name risto, and the occurrence time of the input 
event will be recorded into the operation. 
Note that for event occurrence time SEC always uses the current time 
as returned by the
.BR time (2)
system call, *not* the timestamp extracted from the event. 
.PP
Suppose that after 25 seconds, 
a similar SSH login failure event for the same user name is observed. In this
case, a running operation will be found for the operation description string
.IR "Three SSH login failures within 1m for user risto" ,
and the occurrence time of the second event is recorded into the operation.
If after 30 seconds a third event for the user name risto is observed, 
the operation has processed 3 events within 55 seconds. Since the threshold
condition "3 events within 60 seconds" (as defined by the
.I thresh
and
.I window
fields) is now satisfied, SEC will execute the action defined with the
.I action 
field -- it will fork a command 
.PP
/bin/mail -s 'SSH login alert' root@localhost 
.PP
with a pipe connected to its standard input. Then, SEC writes the operation 
description string 
.I "Three SSH login failures within 1m for user risto"
(held by the %s special variable)
to the standard input of the command through the pipe.
In other words, an e-mail warning is sent to the local root-user. 
Finally, since there are 5 seconds left until the end of
the event correlation window, the operation will consume the following SSH
login failure events for user risto without any further action, and finish 
after 5 seconds.
.PP
The above example illustrates that the
.I desc
field of a rule defines the scope of event correlation and influences the
number of operations created by the rule. For example, if we set the
.I desc 
field to 
.IR "Three SSH login failures within 1m" ,
the root-user would be also alerted on 3 SSH login failure events 
for *different* users within 1 minute. 
In order to avoid clashes between operations started by different rules, 
operation ID contains not only the value set by the
.I desc
field, but also the rule file name and the rule number inside the file.
For example, if the rule file /etc/sec/sshd.rules contains one rule
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from [\\d.]+ port \\d+ ssh2
.br
desc=Three SSH login failures within 1m for user $1
.br
action=pipe '%s' /bin/mail -s 'SSH login alert' root@localhost
.br
window=60
.br
thresh=3
.PP
and the event
.PP
Dec 16 16:24:59 myserver sshd[13685]: Failed password for risto from 10.12.2.5 port 41063 ssh2
.PP
is the first matching event for the above rule, this event will trigger
a new event correlation operation with the ID
.PP
/etc/sec/sshd.rules | 0 | Three SSH login failures within 1m for user risto
.PP
(0 is the number assigned to the first rule in the file, 
see EVENT CORRELATION OPERATIONS section for more information).
.PP
The following simple example demonstrates that event correlation schemes
can be defined by combining several rules. In this example, two rules
harness contexts and synthetic events for achieving their goal:
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from [\\d.]+ port \\d+ ssh2
.br
desc=Three SSH login failures within 1m for user $1
.br
action=event 3_SSH_LOGIN_FAILURES_FOR_$1
.br
window=60
.br
thresh=3
.PP
type=EventGroup
.br
ptype=RegExp
.br
pattern=3_SSH_LOGIN_FAILURES_FOR_(\\S+)
.br
context=!USER_$1_COUNTED && !COUNTING_OFF
.br
count=create USER_$1_COUNTED 60
.br
desc=Repeated SSH login failures for 30 distinct users within 1m
.br
action=pipe '%s' /bin/mail -s 'SSH login alert' root@localhost; \\
       create COUNTING_OFF 3600
.br
window=60
.br
thresh=30
.PP
The first rule looks almost identical to the rule from the previous example, 
but its
.I action
field is different -- after three SSH login failures have been observed for 
the same user name within one minute by an event correlation operation, 
the operation will emit the synthetic event 
3_SSH_LOGIN_FAILURES_FOR_<username>. Although synthetic events are created
by SEC, they are treated like regular events received from input sources and 
are matched against rules. 
.PP
The regular expression pattern of the second rule will match the
3_SSH_LOGIN_FAILURES_FOR_<username> event and start a new event correlation
operation if no such events have been previously seen.  
Also, each time a synthetic event for some user name has matched the rule, 
a context with the lifetime of 1 minute for that user name is created (see the 
.I count
field). 
Note that this prevents further matches for the same user name, since 
a synthetic event for <username> can match the rule only if the context
USER_<username>_COUNTED *does not* exist (as requested by the boolean
expression in the
.I context
field; see CONTEXTS AND CONTEXT EXPRESSIONS section for more information). 
.PP
The operation started by the second rule sends an e-mail warning to the local 
root-user if 30 synthetic events have been observed within 1 minute (see the
.I thresh
and
.I window
fields). Note that due to the use of the USER_<username>_COUNTED contexts, all 
synthetic events concern different user names. After sending an e-mail warning,
the operation will also create the context COUNTING_OFF with the lifetime of
1 hour, and will continue to run until the 1 minute event correlation
window expires. After the operation has finished, the presence of the
COUNTING_OFF context will keep the second rule disabled (as requested by 
the boolean expression in the
.I context
field). Therefore, at most one e-mail warning per 1 hour is issued by 
above rules.
.PP
The above examples have presented the event correlation capabilities of SEC 
in a very brief fashion.
The following sections will provide an in-depth  discussion of SEC features.
.SH OPTIONS
.TP
.B \-\-conf=<file_pattern>
expand <file_pattern> to filenames (with the Perl 
.BR glob () 
function) and read event correlation rules from every file. Multiple
.B \-\-conf
options can be specified at command line. Each time SEC receives a signal
that forces a configuration reload, <file_pattern> is re-evaluated. See also
INPUT PROCESSING AND TIMING section for a discussion on rule processing order 
for multiple configuration files.
.TP 
.B \-\-input=<file_pattern>[=<context>]
expand <file_pattern> to filenames (with the Perl
.BR glob ()
function) and use the files as input sources. An input file can be a regular 
file, named pipe, or standard input if 
.B \-
was specified. Multiple
.B \-\-input
options can be specified at command line. Each time SEC receives the 
.B SIGHUP
or
.B SIGABRT
signal, <file_pattern> is re-evaluated.
If SEC experiences a system error when reading from an input file, it will
close the file (use the
.B \-\-reopen\-timeout
option for reopening the file). If <context> is given, SEC will set up the 
context <context> each time it reads a line from input files that correspond
to <file_pattern>. This will help the user to write rules that match data from
particular input source(s) only. When there is an
.B \-\-input
option with <context> specified, it will automatically enable the
.B \-\-intcontexts
option. See INTERNAL EVENTS AND CONTEXTS section for more information.
.TP 
.BR \-\-input\-timeout=<input_timeout> ", " \-\-timeout\-script=<timeout_script>
if SEC has not observed new data in an input file during <input_timeout>
seconds (or the file was closed <input_timeout> seconds ago), <timeout_script> 
will be executed with command line parameters 1 and <the name of the input 
file>. If fresh data become available again, <timeout_script> will be executed
with command line parameters 0 and <the name of the input file>. 
Setting <input_timeout> to 0 disables this behavior (this is also the default). 
Note that
.B \-\-input_timeout 
and 
.B \-\-timeout_script
options can be used as synonyms for 
.B \-\-input\-timeout 
and 
.BR \-\-timeout\-script ,
respectively.
.TP 
.B \-\-reopen\-timeout=<reopen_timeout> 
if an input file is in the closed state (e.g., SEC fails to open the file at 
startup, because it has not been created yet), SEC will attempt
to reopen the file after every <reopen_timeout> seconds until open succeeds. 
Setting <reopen_timeout> to 0 disables this behavior (this is also the default). 
This option has no meaning when the
.B \-\-notail
option is also specified.
Note that 
.B \-\-reopen_timeout
is a synonym for
.BR \-\-reopen\-timeout .
.TP
.B \-\-check\-timeout=<check_timeout>
if SEC has not observed new data in an input file, the file will not be polled
(both for status and data) during the next <check_timeout> seconds.
Setting <check_timeout> to 0 disables this behavior (this is also the default). 
Note that 
.B \-\-check_timeout
is a synonym for
.BR \-\-check\-timeout .
.TP
.B \-\-poll\-timeout=<poll_timeout>
a real number that specifies how many seconds SEC will sleep when no new data 
were read from input files. Default is 0.1 seconds.
Note that 
.B \-\-poll_timeout
is a synonym for
.BR \-\-poll\-timeout .
.TP
.B \-\-socket\-timeout=<socket_timeout>
if a network connection to a remote peer can't be established within 
<socket_timeout> seconds, give up. Default is 60 seconds.
Note that 
.B \-\-socket_timeout
is a synonym for
.BR \-\-socket\-timeout .
.TP
.B \-\-blocksize=<io_block_size>
the number of bytes SEC will attempt to read at once from an input file. 
Default is 8192 bytes (i.e., read from input files by 8KB blocks).
.TP 
.B \-\-bufsize=<input_buffer_size>
set all input buffers to hold <input_buffer_size> lines. 
The content of input buffers will be compared with 
patterns that are part of rule definitions (i.e., no more than 
<input_buffer_size> lines can be matched by a pattern at a time). 
If <input_buffer_size> is set to 0, SEC will determine the proper value
for <input_buffer_size> by checking event matching patterns of all SEC rules.
Default is 0 (i.e., determine the size of input buffers automatically).
.TP
.B \-\-evstoresize=<event_store_size>
set an upper limit to the number of events in context event stores. 
Default is 0 which sets no limit.
.TP 
.B \-\-cleantime=<clean_time>
time interval in seconds that specifies how often internal event correlation
and context lists are processed, in order to accomplish time-related tasks
and to remove obsolete elements. See INPUT PROCESSING AND TIMING section for 
more information.
Default is 1 second.
.TP 
.B \-\-log=<logfile>
use <logfile> for logging SEC activities. Note that if the SEC standard error
is connected to a terminal, messages will also be logged there, in order to
facilitate debugging.
.TP
.B \-\-syslog=<facility>
use syslog for logging SEC activities. All messages will be logged with the 
facility <facility>, e.g., 
.I local0
(see 
.BR syslog (3)
for possible facility values). Warning: be careful with using this option if 
SEC is employed for monitoring syslog log files, because message loops might
occur.
.TP
.B \-\-debug=<debuglevel>
set logging verbosity for SEC. Setting debuglevel to <debuglevel> 
means that all messages of level <debuglevel> and lower are logged (e.g.,
if <debuglevel> is 3, messages from levels 1-3 are logged). The
following levels are recognized by SEC:
.br
1 - critical messages (severe faults that cause SEC to terminate, e.g., 
a failed system call)
.br
2 - error messages (faults that need attention, e.g., an incorrect rule 
definition in a configuration file)
.br
3 - warning messages (possible faults, e.g., a command forked from SEC 
terminated with a non-zero exit code)
.br
4 - notification messages (normal system level events and interrupts, e.g., 
the reception of a signal)
.br
5 - informative messages (information about external programs forked 
from SEC)
.br
6 - debug messages (detailed information about all SEC activities)
.br
Default <debuglevel> is 6 (i.e., log everything). See SIGNALS section
for information on how to change <debuglevel> at runtime.
.TP 
.B \-\-pid=<pidfile>
SEC will store its process ID to <pidfile> at startup.
.TP
.B \-\-dump=<dumpfile>
SEC will use <dumpfile> as its dump file for writing performance and debug
data. With the
.B \-\-dumpfts
option, a timestamp suffix is appended to the dump file name. With the
.B \-\-dumpfjson
option, dump file is produced in JSON format.
See SIGNALS section for more information. Default is /tmp/sec.dump.
.TP
.BR \-\-user=<username> ", " \-\-group=<groupname>
if SEC is started with effective user ID 0, it will drop root privileges by 
switching to user <username> and group <groupname>.
The
.B \-\-group
option can't be used without the
.B \-\-user
option. If the
.B \-\-user
option is given without
.BR \-\-group ,
primary group of the user <username> is assumed for <groupname>. 
If several groups are provided with multiple
.B \-\-group
options, SEC switches to the first group with other groups as supplementary 
groups.
.TP
.B \-\-umask=<mode>
set file mode creation mask to <mode> at SEC startup, where <mode> 
is a value from the range 0..0777 (see also
.BR umask (2)). 
Octal, decimal, hexadecimal, and binary values can be specified for <mode> 
(e.g., octal mask 0027 can also be expressed as 23, 0x17, and 0b000010111).
.TP
.BR \-\-ruleperf ", " \-\-noruleperf
if the
.B \-\-ruleperf
option is specified, performance data (e.g., total consumed CPU time)
is collected for each rule and reported in dump file. Default is
.BR \-\-noruleperf .
.TP
.BR \-\-dumpfts ", " \-\-nodumpfts
if the
.B \-\-dumpfts
option is specified, a timestamp suffix (seconds since Epoch) is appended
to the dump file name that reflects the file creation time. Default is
.BR \-\-nodumpfts . 
.TP
.BR \-\-dumpfjson ", " \-\-nodumpfjson
if the
.B \-\-dumpfjson
option is specified, dump file is produced in JSON format. 
Default is
.BR \-\-nodumpfjson . 
.TP
.BR \-\-quoting ", " \-\-noquoting 
if the
.B \-\-quoting
option is specified, operation description strings that are supplied to 
command lines of
.IR shellcmd ,
.IR spawn ,
and
.I cspawn
actions will be put inside single quotes. Each single quote (') that strings 
originally contain will be masked. This option prevents the shell from 
interpreting special symbols that operation description strings might contain. 
Default is
.BR \-\-noquoting .
.TP 
.BR \-\-tail ", " \-\-notail
if the
.B \-\-notail
option is specified, SEC will process all data that are currently available 
in input files and exit after reaching all EOFs. 
If all input is received from a pipe and the
.B \-\-notail
option is given, SEC terminates when the last writer closes the pipe 
(EOF condition). Please note that with named pipes
.B \-\-notail
should be used with
.BR \-\-norwfifo .
With the
.B \-\-tail
option, SEC will jump to the end of input files and wait for new lines to 
arrive.
Each input file is tracked both by its name and i-node, and
input file rotations are handled seamlessly.
If the input file is recreated or truncated, SEC will reopen it and process 
its content from the beginning. If the input file is removed (i.e., there is
just an i-node left without a name), SEC will keep the i-node open and wait 
for the input file recreation. 
Default is
.BR \-\-tail .
.TP 
.BR \-\-fromstart ", " \-\-nofromstart
these flags have no meaning when the
.B \-\-notail
option is also specified. When used in combination with
.B \-\-tail
(or alone, since
.B \-\-tail
is enabled by default),
.B \-\-fromstart
will force SEC to read and process input files from the beginning to 
the end, before the 'tail' mode is entered. Default is 
.BR \-\-nofromstart .
.TP 
.BR \-\-detach ", " \-\-nodetach
if the
.B \-\-detach
option is specified, SEC will disassociate itself from the controlling
terminal and become a daemon at startup (note that SEC will close its standard 
input, standard output, and standard error, and change its working directory
to the root directory). Default is 
.BR \-\-nodetach .
.TP
.BR \-\-jointbuf ", " \-\-nojointbuf
if the
.B \-\-jointbuf
option is specified, SEC uses joint input buffer for all input sources
(the size of the buffer is set with the
.B \-\-bufsize
option). The
.B \-\-nojointbuf
option creates a separate input buffer for each input file, and a separate
buffer for all synthetic and internal events (the sizes of all buffers are 
set with the
.B \-\-bufsize
option). The
.B \-\-jointbuf
option allows multiline patterns to match lines from several input 
sources, while the
.B \-\-nojointbuf 
pattern restricts the matching to lines from one input source only.
See INPUT PROCESSING AND TIMING section for more information.
If the size of input buffer(s) is 1 (either explicitly set with
.B \-\-bufsize=1
or automatically determined from SEC rules),
.B \-\-jointbuf
option is enabled, otherwise the default is 
.BR \-\-nojointbuf .
.TP
.BR \-\-keepopen ", " \-\-nokeepopen
if the
.B \-\-keepopen
option is specified, SEC will keep input files open across soft restarts.
When the
.B SIGABRT
signal is received, SEC will not reopen input files which have been opened
previously, but will only open input files which are in the closed state.
The 
.B \-\-nokeepopen 
option forces SEC to close and (re)open all input files during soft restarts.
Default is
.BR \-\-keepopen .
.TP
.BR \-\-rwfifo ", " \-\-norwfifo
if the
.BR \-\-norwfifo
option is specified, named pipe input files are opened in read-only mode. 
In this mode, the named pipe has to be reopened when the last writer
closes the pipe, in order to clear the EOF condition on the pipe. With the
.BR \-\-rwfifo
option, named pipe input files are opened in read-write mode, although
SEC never writes to the pipes. In this mode, the pipe does not need to be 
reopened when an external writer closes it, since there is always at least 
one writer on the pipe and EOF will never appear. Therefore, if the
.BR \-\-notail
option has been given,
.BR \-\-norwfifo
should also be specified.
Default is
.BR \-\-rwfifo .
.TP
.BR \-\-childterm ", " \-\-nochildterm
if the
.B \-\-childterm
option is specified, SEC will send the 
.B SIGTERM 
signal to all its child processes
when it terminates or goes through a full restart. Default is
.BR \-\-childterm . 
.TP
.BR \-\-intevents ", " \-\-nointevents
SEC will generate internal events when it starts up, when it receives
certain signals, and when it terminates gracefully. Specific rules can be 
written to match those internal events, in order to accomplish special
tasks at SEC startup, restart, and shutdown. 
See INTERNAL EVENTS AND CONTEXTS section for more information. Default is
.BR \-\-nointevents .
.TP
.BR \-\-intcontexts ", " \-\-nointcontexts
SEC will create an internal context when it reads a line from an input file.
This will help the user to write rules that match data from particular input 
source only. See INTERNAL EVENTS AND CONTEXTS section for more information. 
Default is
.BR \-\-nointcontexts .
.TP
.BR \-\-testonly ", " \-\-notestonly
if the
.B \-\-testonly
option is specified, SEC will exit immediately after parsing the configuration 
file(s). If the configuration file(s) contained no faulty rules, SEC will exit 
with 0, otherwise with 1. Default is
.BR \-\-notestonly .
.TP
.BR \-\-help ", " \-?
SEC will output usage information and exit.
.TP
.B \-\-version
SEC will output version information and exit.
.PP
Note that options can be introduced both with the single dash (-) and double
dash (--), and both the equal sign (=) and whitespace can be used for 
separating the option name from the option value. For example,
.B \-conf=<file_pattern>
and
.B \-\-conf <file_pattern>
options are equivalent.
.SH CONFIGURATION FILES
Each SEC configuration file consists of rule definitions which are separated 
by empty lines, whitespace lines and/or comment lines.
Each rule definition consists of keyword=value fields, one keyword and value 
per line. Values are case insensitive only where character case is not 
important (like the values specifying rule types, e.g., 'Single' and 'single'
are treated identically).
The backslash character (\\) may be used at the end of a line to continue 
the current rule field in the next line. 
Lines which begin with the number sign (#) are treated as comments and 
ignored (whitespace characters may precede #). Any comment line, 
empty line, whitespace line, or end of file will terminate the preceding 
rule definition.
For inserting comments into rule definitions, the
.I rem
keyword can be used. For example, the following lines define two rules:
.PP
type=Single
.br
rem=this rule matches any line which contains \\
    three consecutive A characters and writes the string \\
    "three A characters were observed" to standard output
.br
ptype=SubStr
.br
pattern=AAA
.br
desc=Three A characters
.br
action=write - three A characters were observed
.br
# This comment line ends preceding rule definition.
.br
# The following rule works like the previous rule,
.br
# but looks for three consecutive B characters and
.br
# writes the string "three B characters were observed"
.br
# to standard output
.br
type=Single
.br
ptype=SubStr
.br
pattern=BBB
.br
desc=Three B characters
.br
action=write - three B characters were observed
.PP
Apart from keywords that are part of rule definitions, 
.I label
keywords may appear anywhere in the configuration file. The value of each
.I label
keyword will be treated as a label that can be referred to in rule definitions
as a point-of-continue.
This allows for continuing event processing at a rule that follows the label,
after the current rule has matched and processed the event.
.PP
The points-of-continue are defined with
.I continue*
fields. Accepted values for these fields are:
.TP
.I TakeNext 
after an event has matched the rule, search for matching rules
in the configuration file will continue from the next rule.
.TP
.I GoTo <label>
after an event has matched the rule, search for matching rules will continue
from the location of <label> in the configuration file (<label> must
be defined with the 
.I label
keyword anywhere in the configuration file *after* the current rule 
definition).
.TP
.IR DontCont " (default value)"
after an event has matched the rule, search for matching rules ends 
in the *current* configuration file.
.TP
.I EndMatch
after an event has matched the rule, search for matching rules ends 
for *all* configuration files.
.PP
SEC rules from the same configuration file are matched against input 
in the order they have been given in the file.
For example, consider a configuration file which contains the following 
rule sequence:
.PP
type=Single
.br
ptype=SubStr
.br
pattern=AAA
.br
rem=after this rule has matched, continue from last rule
.br
continue=GoTo lastRule
.br
desc=Three A characters
.br
action=write - three A characters were observed
.PP
type=Single
.br
ptype=SubStr
.br
pattern=BBB
.br
rem=after this rule has matched, don't consider following rules, \\
    since 'continue' defaults to 'DontCont'
.br
desc=Three B characters
.br
action=write - three B characters were observed
.PP
type=Single
.br
ptype=SubStr
.br
pattern=CCC
.br
rem=after this rule has matched, continue from next rule
.br
continue=TakeNext
.br
desc=Three C characters
.br
action=write - three C characters were observed
.PP
label=lastRule
.PP
type=Single
.br
ptype=SubStr
.br
pattern=DDD
.br
desc=Three D characters
.br
action=write - three D characters were observed
.PP
For the input line "AAABBBCCCDDD", this ruleset writes strings
"three A characters were observed" and "three D characters were observed"
to standard output. If the input line is "BBBCCCDDD", the string
"three B characters were observed" is written to standard output.
For the input line "CCCDDD", strings "three C characters were observed"
and "three D characters were observed" are sent to standard output, while
the input line "DDD" produces the output string 
"three D characters were observed".
.PP
If there are two or more configuration files, rule sequence from every file 
is matched against input (unless explicitly specified otherwise). 
For example, suppose SEC is started with the command line
.PP
/usr/bin/sec --input=- \\
             --conf=/etc/sec/sec1.rules --conf=/etc/sec/sec2.rules
.PP
and the configuration file /etc/sec/sec1.rules has the following content:
.PP
type=Single
.br
ptype=SubStr
.br
pattern=AAA
.br
desc=Three A characters
.br
action=write - three A characters were observed
.PP
type=Single
.br
ptype=SubStr
.br
pattern=BBB
.br
continue=EndMatch
.br
desc=Three B characters
.br
action=write - three B characters were observed
.PP
Also, suppose the  configuration file /etc/sec/sec2.rules has the following 
content:
.PP
type=Single
.br
ptype=SubStr
.br
pattern=CCC
.br
desc=Three C characters
.br
action=write - three C characters were observed
.PP
If SEC receives the line "AAABBBCCC" from standard input, rules from both
configuration files are tried, and as a result, the strings
"three A characters were observed" and "three C characters were observed"
are written to standard output. Note that rules from /etc/sec/sec1.rules
are tried first against the input line, since the option
.B --conf=/etc/sec/sec1.rules 
is given before 
.B --conf=/etc/sec/sec2.rules 
in the SEC command line (see also INPUT PROCESSING AND TIMING section for 
a more detailed discussion).
If SEC receives the line "BBBCCC" from standard input, the second rule
from /etc/sec/sec1.rules produces a match, and the string
"three B characters were observed" is written to standard output.
Since the rule contains
.I continue=EndMatch
statement,
the search for matching rules will end for all configuration files, and
rules from /etc/sec/sec2.rules will not be not tried. Without this statement,
the search for matching rules would continue in /etc/sec/sec2.rules,
and the first rule would write the string "three C characters were observed"
to standard output.
.SH "PATTERNS, PATTERN TYPES AND MATCH VARIABLES"
Patterns and pattern types are defined with 
.I pattern*
and
.I ptype*
rule fields.
Many pattern types define the number of lines 
.I N 
which the pattern matches (if 
.I N 
is omitted, 1 is assumed). If
.I N
is greater than 1, the scope of matching is set with the 
.B \-\-jointbuf
and
.B \-\-nojointbuf
options.
With 
.BR \-\-jointbuf ,
the pattern is used for matching 
.I N 
last input lines taken from the joint input buffer (the lines can come from 
different input sources).
With 
.BR \-\-nojointbuf ,
the source of the last input line is identified, and the pattern
is matched with 
.I N 
last input lines from the input buffer of the identified source.
.TP
.I SubStr[N]
pattern is a string that is searched in the last N input lines 
L1, L2, ..., LN. If N is greater than 1, the input lines are joined into 
a string "L1<NEWLINE>L2<NEWLINE>...<NEWLINE>LN", and the pattern
string will be searched from it.
If the pattern string is found in input line(s), the pattern matches.
Backslash sequences \\t, \\n, \\r, \\s, and \\0 can be used in the
pattern for denoting tabulation, newline, carriage return, space character, 
and empty string, respectively, while \\\\ denotes backslash itself. 
For example, consider the following pattern definition:
.sp
ptype=substr
.br
pattern=Backup done:\\tsuccess
.sp
The pattern matches lines containing "Backup done:<TAB>success".
.sp
Note that since the
.I SubStr[N]
pattern type has been designed for fast matching, it does not support match 
variables.
.TP
.I RegExp[N]
pattern is a Perl regular expression (see 
.BR perlre (1)
for more information) for matching the last N input lines 
L1, L2, ..., LN. If N is greater than 1, the input lines are joined into 
a string "L1<NEWLINE>L2<NEWLINE>...<NEWLINE>LN", and the regular expression 
is matched with this string.
If the regular expression matches, match variables will be set, and these
match variables can be used in other parts of the rule definition. 
.sp
In addition to numbered match variables ($1, $2, etc.), SEC supports named
match variables $+{name} and the $0 variable. The $0 variable holds the entire 
string of last N input lines that the regular expression has matched. 
Named match variables can be created in newer versions of Perl regular 
expression language, e.g., 
(?<myvar>AB|CD) sets $+{myvar} to AB or CD. Also, SEC creates special named match 
variables $+{_inputsrc} and $+{_intcontext}. The $+{_inputsrc} variable holds input 
file name(s) where matching line(s) came from. The $+{_intcontext} variable holds
the name of current internal context (see INTERNAL EVENTS AND CONTEXTS section
for more information). If internal context has not been set up for
the current input source, the variable is set to Perl undefined value.
.sp
For example, the following pattern matches the SSH "Connection from" event,
and sets $0 to the entire event line, both $1 and $+{ip} to the IP address 
of the remote node, and $2 to the port number at the remote node:
.sp
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Connection from (?<ip>[\\d.]+) port (\\d+)
.sp
If the matching event comes from input file /var/log/messages with internal 
context MSGS, the $+{_inputsrc} and $+{_intcontext} variables are set to 
strings "/var/log/messages" and "MSGS", respectively.
.sp
Also, SEC allows for match caching and for the creation of additional named 
match variables through variable maps which are defined with the
.I varmap*
fields. Variable map is a list of 
.I name=number 
mappings separated by semicolons, where
.I name
is the name for the named variable and 
.I number 
identifies a numbered match
variable that is set by the regular expression. 
Each name must begin with
a letter and consist of letters, digits and underscores. After the regular 
expression has matched, named variables specified by the map are created from 
corresponding numbered variables. If the same named variable is set up both 
from the regular expression and variable map, the map takes precedence. 
.sp
If 
.I name
is not followed by the equal sign and number in the
.I varmap*
field, it is regarded as a common name for all match variables and their 
values from a successful match.
This name is used for caching a successful match by the pattern -- 
match variables and their values are stored in the memory-based 
pattern match cache under 
.IR name . 
Cached match results can be reused by
.I Cached
and 
.I NCached
patterns. Note that before processing each new input line, previous
content of the pattern match cache is cleared. Also note that a successful
pattern match is cached even if the subsequent context expression evaluation
yields FALSE (see INPUT PROCESSING AND TIMING section for more information).
.sp
For example, consider the following pattern definition:
.sp
ptype=regexp
.br
pattern=(?i)(\\S+\\.mydomain).*printer: toner\\/ink low
.br
varmap=printer_toner_or_ink_low; message=0; hostname=1
.sp
The pattern matches "printer: toner/ink low" messages in a case insensitive
manner from printers belonging to .mydomain. Note that the printer hostname
is assigned to $1 and $+{hostname}, while the whole message line is assigned 
to $0 and $+{message}. If the message comes from file /var/log/test which does
not have an internal context defined, the $+{_inputsrc} variable is set to
string "/var/log/test", while $+{_intcontext} is set to Perl undefined value.
Also, these variables and their values are stored to the pattern match cache 
under the name "printer_toner_or_ink_low".
.sp
The following pattern definition produces a match if the last two input lines
are AAA and BBB:
.sp
ptype=regexp2
.br
pattern=^AAA\\nBBB$
.br
varmap=aaa_bbb
.sp
Note that with the
.B \-\-nojointbuf
option the pattern only matches if the matching lines are coming from 
the *same* input file, while the
.B \-\-jointbuf
option lifts that restriction.
.sp
In the case of a match, $0 is set to "AAA<NEWLINE>BBB", $+{_inputsrc} to file name(s) 
for matching lines, and $+{_intcontext} to the name of current internal context. 
Also, these variable-value pairs are cached under the name "aaa_bbb".
.TP
.I PerlFunc[N]
pattern is a Perl function for matching the last N input lines
L1, L2, ..., LN. The Perl function is compiled at SEC startup with
the Perl
.BR eval ()
function, and 
.BR eval ()
must return a code reference for the pattern to be valid 
(see also PERL INTEGRATION section). 
The function is called in Perl list context, and with the
.B \-\-jointbuf
option, lines L1, L2, ..., LN and the names of corresponding input files 
F1, F2, ..., FN are passed to the function as parameters: 
.sp
function(L1, L2, ..., LN, F1, F2, ..., FN) 
.sp
Note that with the
.B \-\-nojointbuf
option, the function is called with a single file name parameter F, since
lines L1, ..., LN are coming from the same input file:
.sp
function(L1, L2, ..., LN, F)
.sp
Also note that if the input line is a synthetic event, the input file name 
is Perl undefined value.
.sp
If the function returns several values or a single value that is true in Perl
boolean context, the pattern matches. If the function returns no values or
a single value that is false in Perl boolean context (0, empty string or 
undefined value), the pattern does not match. If the pattern matches, 
return values will be assigned to numbered match variables ($1, $2, etc.). 
Like with RegExp patterns, the $0 variable is set to matching input line(s),
the $+{_inputsrc} variable is set to input file name(s),
the $+{_intcontext} variable is set to the name of current internal context,
and named match variables can be created from variable maps.
For example, consider the following pattern definition:
.sp
ptype=perlfunc2
.br
pattern=sub { return ($_[0] cmp $_[1]); }
.sp
The pattern compares last two input lines in a stringwise manner ($_[1] 
holds the last line and $_[0] the preceding one), and matches if the lines
are different. Note that the result of the comparison is assigned to $1,
while two matching lines are concatenated (with the newline character
between them) and assigned to $0. 
If matching lines come from input file /var/log/mylog with internal 
context TEST, the $+{_inputsrc} and $+{_intcontext} variables are set to
strings "/var/log/mylog" and "TEST", respectively.
.sp
The following pattern produces a match for any line, and sets $1, $2 and
$3 variables to strings "abc", "def" and "ghi", respectively (also,
$0 is set to the whole input line, $+{_inputsrc} to the input file name,
and $+{_intcontext} to the name of internal context associated with input
file $+{_inputsrc}):
.sp
ptype=perlfunc
.br
pattern=sub { return ("abc", "def", "ghi"); }
.sp
The following pattern definition produces a match if the input line is not
a synthetic event and contains either the string "abc" or "def". The $0 
variable is set to the matching line. If matching line comes from /var/log/test
without an internal context, $+{_intcontext} is set to Perl undefined value,
while $1, $+{file} and $+{_inputsrc} are set to string "/var/log/test":
.sp
ptype=perlfunc
.br
pattern=sub { if (defined($_[1]) && $_[0] =~ /abc|def/) \\
.br
{ return $_[1]; } return 0; }
.br
varmap= file=1
.sp
Finally, if a function pattern returns a single value which is a reference
to a Perl hash, named match variables are created from key-value pairs 
in the hash. For example, the following pattern matches a line if it contains
either the string "three" or "four". Apart from setting $0, $+{_inputsrc}
and $+{_intcontext}, the pattern also creates match variables $+{three} and $+{four}, 
and sets them to 3 and 4, respectively:
.sp
ptype=perlfunc
.br
pattern=sub { my(%hash); \\
.br
if ($_[0] !~ /three|four/) { return 0; } \\
.br
$hash{"three"} = 3; $hash{"four"} = 4; return \\%hash; }
.TP
.I Cached
pattern is a name that is searched in the pattern match cache (entries are
stored into the cache with the
.I varmap*
fields). If an entry with the given name is found in the cache, the pattern
matches, and match variables and values are retrieved from the cache.
For example, if the input line matches the following pattern
.sp
ptype=perlfunc
.br
pattern=sub { if (defined($_[1]) && $_[0] =~ /abc|def/) \\
.br
{ return $_[1]; } return 0; }
.br
varmap=abc_or_def_found; file=1
.sp
then the entry "abc_or_def_found" is created in the pattern match cache.
Therefore, the pattern 
.sp
ptype=cached
.br
pattern=abc_or_def_found
.sp
will also produce a match for this input line, and set the $0, $1, $+{file}, 
$+{_inputsrc}, and $+{_intcontext} variables to values from the previous match.
.TP
.I NSubStr[N]
like
.IR SubStr[N] ,
except that the result of the match is negated.
Note that this pattern type does not support match variables.
.TP
.I NRegExp[N]
like
.IR RegExp[N] ,
except that the result of the match is negated and variable maps are not 
supported. Note that the only match variables supported by this pattern type 
are $0, $+{_inputsrc}, and $+{_intcontext}.
.TP
.I NPerlFunc[N]
like
.IR PerlFunc[N] ,
except that the result of the match is negated and variable maps are not
supported. Note that the only match variables supported by this pattern type 
are $0, $+{_inputsrc}, and $+{_intcontext}.
.TP
.I NCached
like
.IR Cached ,
except that the result of the match is negated. 
Note that this pattern type does not support match variables.
.TP
.I TValue
pattern is a truth value, with TRUE and FALSE being legitimate values. 
TRUE always matches an input line, while FALSE never matches anything.
Note that this pattern type does not support match variables.
.PP
When match variables are substituted, each "$$" sequence is interpreted as
a literal dollar sign ($) which allows for masking match variables. 
For example, the string "Received $$1" becomes "Received $1" after 
substitution, while "Received $$$1" becomes "Received $<value_of_1st_var>". 
In order to disambiguate numbered match variables from the following text, 
variable number must be enclosed in braces. For example, the string 
"Received ${1}0" becomes "Received <value_of_1st_var>0" after substitution, 
while the string "Received $10" would become "Received <value_of_10th_var>".
.PP
If the match variable was not set by the pattern, it is substituted with an 
empty string (i.e., a zero-width string). 
Thus the string "Received $10!" becomes "Received !" after substitution if
the pattern did not set $10.
(Note that prior to SEC-2.6, unset variables were *not* substituted.)
.PP
In the current version of SEC, names of $+{name} match variables
must comply with the following naming convention -- the first character 
can be a letter or underscore, while remaining characters can be letters, 
digits, underscores and exclamation marks (!). However, when setting named 
match variables from a pattern, it is recommended to begin the variable 
name with a letter, since names of special automatically created variables 
begin with an underscore (e.g., $+{_inputsrc}).
.PP
After the pattern has matched an event and match variables have been set, 
it is also possible to refer to previously cached match variables with 
the syntax 
.IR $:{entryname:varname} , 
where
.I entryname
is the name of the pattern match cache entry, and
.I varname
is the name of the variable stored under the entry. 
For example, if the variable $+{ip} has been previously cached under 
the entry "SSH", it can be referred as $:{SSH:ip}.
For the reasons of efficiency, the $:{entryname:varname} syntax is not 
supported for fast pattern types which do not set match variables (i.e., 
SubStr, NSubStr, NCached and TValue).
.PP
Note that since Pair and PairWithWindow rules have two patterns, match
variables of the first pattern are shadowed for some rule fields when the 
second pattern matches and sets variables. In order to refer to shadowed 
variables, their names
must begin with % instead of $ (e.g., %1 refers to match variable $1 set by
the first pattern). However, the use of the %-prefix is only valid under the 
following circumstances -- *both* pattern types support match variables *and* 
in the given rule field match variables from *both* patterns can be used.
.PP
The %-prefixed match variables are masked with the "%%" sequence (like 
regular match variables with "$$"). Similarly, the braces can be
used for disambiguating the %-prefixed variables from the following text.
.PP
Finally, note that the second pattern of Pair and PairWithWindow rules may 
contain match variables if the second pattern is of type SubStr, NSubStr, 
Regexp, or NRegExp. The variables are substituted at runtime with the values 
set by the first pattern. If the pattern is a regular expression, all 
special characters inside substituted values are masked with the Perl
.BR quotemeta ()
function and the final expression is checked for correctness.
.SH "CONTEXTS AND CONTEXT EXPRESSIONS"
A SEC context is a memory based entity which has one or more names,
a lifetime, and an event store. Also, an action list can be set up
for a context which is executed immediately before the context expires.
.PP
For example, the action
.I create MYCONTEXT 3600 (report MYCONTEXT /bin/mail root@localhost)
creates the context 
.B MYCONTEXT 
which has a lifetime of 3600 seconds and empty event store.
Also, immediately before 
.B MYCONTEXT 
expires and is dropped from memory, the action
.I report MYCONTEXT /bin/mail root@localhost
is executed which mails the event store of 
.B MYCONTEXT 
to root@localhost. 
.PP
Contexts can be used for event aggregation and reporting.
Suppose the following actions are executed in this order:
.PP
create MYCONTEXT 
.br
add MYCONTEXT This is a test
.br
alias MYCONTEXT MYALIAS
.br
add MYALIAS This is another test
.br
report MYCONTEXT /bin/mail root@localhost
.br
delete MYALIAS
.PP
The first action creates the context 
.B MYCONTEXT 
with infinite lifetime
and empty event store. The second action appends the string 
"This is a test" to the event store of 
.BR MYCONTEXT . 
The third action
sets up an alias name 
.B MYALIAS 
for the context (names 
.B MYCONTEXT 
and 
.B MYALIAS
refer to the same context data structure). The fourth action appends
the string "This is another test" to the event store of the context.
The fifth action writes the lines
.PP
This is a test
.br
This is another test
.PP
to the standard input of the
.I /bin/mail root@localhost 
command. The sixth action deletes the context data structure
from memory and drops its names 
.B MYCONTEXT 
and 
.BR MYALIAS .
.PP
Since contexts are accessible from all rules and event correlation operations,
they can be used for data sharing and joining several rules into one event 
correlation scheme.
In order to check for the presence of contexts from rules,
context expressions can be employed.
.PP
Context expressions are boolean expressions that are defined with the
.I context*
rule fields. Context expressions can be used for restricting the matches
produced by patterns, since if the expression evaluates FALSE, the rule will
not match an input event.
.PP
The context expression accepts context names, Perl miniprograms, Perl 
functions, and pattern match cache lookups as operands. These operands can 
be combined with the following operators:
.br
!  - logical NOT, 
.br
&&  - short-circuit logical AND, 
.br
||  - short-circuit logical OR. 
.br
In addition, parentheses can be used for grouping purposes.
.PP
If the operand does not contain any special operators (such as -> or :>,
see below), it is treated as a context name. Context name operands may 
contain match variables, but may not contain whitespace.
If the context name refers to an existing context, the operand evaluates
TRUE, otherwise it evaluates FALSE.
.PP
For example, consider the following rule sequence:
.PP
type=Single
.br
ptype=RegExp
.br
pattern=Test: (\\d+)
.br
desc=test
.br
action=create CONT_$1
.PP
type=Single
.br
ptype=RegExp
.br
pattern=Test2: (\\d+) (\\d+)
.br
context=CONT_$1 && CONT_$2
.br
desc=test
.br
action=write - Both $1 and $2 have been seen in the past
.PP
If the following input lines appear in this order
.PP
Test: 19
.br
Test: 261
.br
Test2: 19 787
.br
Test: 787
.br
Test2: 787 261
.PP
the first input line matches the first rule which creates the context
.BR CONT_19 ,
and similarly, the second input line triggers the creation of the context
.BR CONT_261 .
The third input line "Test2: 19 787" matches the regular expression 
.PP
Test2: (\\d+) (\\d+)
.PP
but does not match the second rule, since the boolean expression
.PP
CONT_19 && CONT_787
.PP
evaluates FALSE (context 
.B CONT_19
exists, but context
.B CONT_787
doesn't). The fourth input line matches the first rule which creates 
the context
.BR CONT_787 .
The fifth input line "Test2: 787 261" matches the second rule, since the
boolean expression
.PP
CONT_787 && CONT_261
.PP
evaluates TRUE (both context
.B CONT_787
and context
.B CONT_261
exist), and therefore the string "Both 787 and 261 have been seen in the past"
is written to standard output.
.PP
If the context expression operand contains the arrow operator (->), the text 
following the arrow must be a valid Perl function definition that is compiled 
at SEC startup with the Perl
.BR eval () 
function. The 
.BR eval () 
must return a code reference (see also PERL INTEGRATION section for more
information). If any text precedes the arrow, it is treated as a list of 
parameters for the function. Parameters must be separated by whitespace and 
may contain match variables.
In order to evaluate the context expression operand, the Perl function is 
called in the Perl scalar context. If the return value of the function is 
true in the Perl boolean context, the operand evaluates TRUE, otherwise it 
evaluates FALSE.
.PP
For example, the following rule matches an SSH login failure event if 
the login attempt comes from a privileged port of the client host:
.PP
type=Single
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from [\\d.]+ port (\\d+) ssh2
.br
context=$2 -> ( sub { $_[0] < 1024 } )
.br
desc=SSH login failure for $1 priv port $2
.br
action=write - SSH login failure for user $1 from a privileged port $2
.PP
When the following message from SSH daemon appears
.PP
Dec 16 16:24:59 myserver sshd[13685]: Failed password for risto from 10.12.2.5 port 41063 ssh2
.PP
the regular expression of the rule matches this message, and the value of 
the $2 match variable (41063) is passed to the Perl function
.PP
sub { $_[0] < 1024 }
.PP
This function returns true if its input parameter is less than 1024 and 
false otherwise, and therefore the above message will not match the rule. 
However, the following message
.PP
Dec 16 16:25:17 myserver sshd[13689]: Failed password for risto from 10.12.2.5 port 1023 ssh2
.PP
matches the rule, and the string "SSH login failure for user risto from 
a privileged port 1023" is written to standard output.
.PP
As another example, the following context expression evaluates TRUE if 
the /var/log/messages file does not exist or was last modified more than 
1 hour ago (note that the Perl function takes no parameters):
.PP
context= -> ( sub { my(@stat) = stat("/var/log/messages"); \\
.br
return (!scalar(@stat) || time() - $stat[9] > 3600); } )
.PP
If the context expression operand contains the :> operator, the text that
follows :> must be a valid Perl function definition that is compiled 
at SEC startup with the Perl
.BR eval () 
function. The 
.BR eval () 
must return a code reference (see also PERL INTEGRATION section for more
information). If any text precedes the :> operator, it is treated as a list 
of parameters for the function. Parameters must be separated by whitespace 
and may contain match variables.
It is assumed that each parameter is a name of an entry in the pattern 
match cache. If an entry with the given name does not exist, Perl undefined
value is passed to the function. If an entry with the given name exists,
a reference to the entry is passed to the Perl function. 
Internally, each pattern match cache entry is implemented as a Perl hash 
which contains all match variables for the given entry. In the hash, each 
key-value pair represents some variable name and value, e.g., if cached 
match variable $+{ip} is holding 10.1.1.1, the hash contains the value
.B 10.1.1.1
with the key
.BR ip .
In order to evaluate the context expression operand, the Perl function is 
called in the Perl scalar context. If the return value of the function is 
true in the Perl boolean context, the operand evaluates TRUE, otherwise it 
evaluates FALSE.
.PP
For example, consider the following rule sequence:
.PP
type=Single
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: (?<status>Accepted|Failed) .+ \\
.br
for (?<invuser>invalid user )?(?<user>\\S+) from (?<ip>[\\d.]+) \\
.br
port (?<port>\\d+) ssh2
.br
varmap=SSH
.br
continue=TakeNext
.br
desc=parse SSH login events and pass them to following rules
.br
action=none
.PP
type=Single
.br
ptype=Cached
.br
pattern=SSH
.br
context=SSH :> ( sub { $_[0]->{"status"} eq "Failed" && \\
                       $_[0]->{"port"} < 1024 && \\
                       defined($_[0]->{"invuser"}) } )
.br
desc=Probe of invalid user $+{user} from privileged port of $+{ip}
.br
action=pipe '%t: %s' /bin/mail -s 'SSH alert' root@localhost
.PP
The first rule matches and parses SSH login messages, and stores parsing
results to the pattern match cache under the name
.BR SSH .
The pattern of the second rule (defined with
.I ptype=Cached
and
.IR pattern=SSH )
matches any input event for which the entry
.B SSH
has been previously created in the pattern match cache (in other words,
the event has been recognized and parsed as an SSH login message).
For each matching event, the second rule passes the reference to the
.B SSH
cache entry to the Perl function
.PP
sub { $_[0]->{"status"} eq "Failed" && \\
      $_[0]->{"port"} < 1024 && \\
      defined($_[0]->{"invuser"}) }
.PP
The function checks the values of $+{status}, $+{port}, and $+{invuser}
match variables under the
.B SSH
entry, and returns true if $+{status} equals to the string "Failed" 
(i.e., login attempt failed), the value of $+{port} is less than 1024, 
and $+{invuser} holds a defined value (i.e., user account does not exist). 
If the function (and thus context expression) evaluates TRUE, the rule sends 
a warning e-mail to root@localhost that a non-existing user account was 
probed from a privileged port of a client host.
.PP
If the context expression operand begins with the
.I varset
keyword, the following string is treated as a name of an entry in the pattern 
match cache. The operand evaluates TRUE if the given entry exists, and FALSE 
otherwise.
.PP
For example, the following context expression definition evaluates TRUE if 
the pattern match cache entry
.B SSH
exists and under this entry, the value of the match variable $+{user}
equals to the string "risto":
.PP
context=varset SSH && SSH :> ( sub { $_[0]->{"user"} eq "risto" } )
.PP
If the context expression operand begins with the equal sign (=), 
the following text must be a Perl miniprogram which is a valid parameter 
for the Perl 
.BR eval ()
function. The miniprogram may contain match variables.
In order to evaluate the Perl miniprogram operand, it will be compiled and 
executed by calling the Perl
.BR eval ()
function in the Perl scalar context (see also PERL INTEGRATION section).
If the return value from 
.BR eval ()
is true in the Perl boolean context, the operand evaluates TRUE, otherwise it
evaluates FALSE. Please note that unlike Perl functions of -> and :> 
operators which are compiled once at SEC startup, Perl miniprograms are
compiled before each execution, and their evaluation is thus considerably
more expensive.
.PP
For example, the following context expression evaluates TRUE when neither 
the context 
.B C1 
nor the context 
.B C2 
exists and the value of the $1 variable equals to the string "myhost.mydomain": 
.PP
context=!(C1 || C2) && =("$1" eq "myhost.mydomain")
.PP
Since && is a short-circuiting operator, the Perl code 
.PP
"$1" eq "myhost.mydomain" 
.PP
is *not* evaluated if either
.B C1
or
.B C2
exists. 
.PP
Note that since Perl functions and miniprograms may contain strings that 
clash with context expression operators (e.g., '!'), it is recommended 
to enclose them in parentheses, e.g.,
.PP
context=$1 $2 -> ( sub { $_[0] != $_[1] } )
.PP
context= =({my($temp) = 0; !$temp;})
.PP
Also, if function parameter lists contain such strings, they should be 
enclosed in parentheses in the similar way:
.PP
context=($1! $2) -> ( sub { $_[0] eq $_[1] } )
.PP
If the whole context expression is enclosed in square brackets [], e.g.,
.RB [ MYCONTEXT1 " && !" MYCONTEXT2 ], 
SEC evaluates the expression *before* pattern matching (normally, the pattern 
is matched with input line(s) first, so that match variables would be 
initialized and substituted before the expression is evaluated). 
However, if the expression does not contain match variables and many input
events are known to match the pattern but not the expression,
the []-operator could save substantial amount of CPU time. 
.SH "ACTIONS, ACTION LISTS AND ACTION LIST VARIABLES"
Action lists are defined with the
.I action*
rule fields. An action list consists of action definitions that are separated 
by semicolons. 
Each action definition begins with a keyword specifying the action type. 
Depending on the action type, parameters may follow, and non-constant
parameters may contain match variables. For instance, if the $1 and $2 match
variables have the values "test1" and "the second test", respectively, 
the action
.I create MYCONT_$1 60
creates the context 
.B MYCONT_test1 
with the lifetime of 60 seconds, while the action
.I write - The names of tests: $1, $2
writes the string "The names of tests: test1, the second test" 
to standard output. 
.PP
Apart from few exceptions explicitly noted, match variables are substituted 
at the earliest opportunity in action lists.
For example, consider the following rule definition:
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from [\\d.]+ port \\d+ ssh2
.br
desc=Three SSH login failures within 1m
.br
action=pipe 'Three SSH login failures, first user is $1' \\
            /bin/mail -s 'SSH login alert' root@localhost
.br
window=60
.br
thresh=3
.PP
When this rule matches an SSH login failure event which starts an event correlation 
operation, the operation substitutes the $1 match variable in the action list definition 
with the user name from the matching event, and user names from further events processed 
by this event correlation operation are not considered for $1. 
For example, if the following events are observed
.PP
Dec 16 16:24:52 myserver sshd[13671]: Failed password for root from 10.12.2.5 port 29736 ssh2
.br
Dec 16 16:24:59 myserver sshd[13685]: Failed password for risto from 10.12.2.5 port 41063 ssh2
.br
Dec 16 16:25:01 myserver sshd[13689]: Failed password for oracle from 10.12.2.5 port 11204 ssh2
.PP
then all events are processed by the same operation, and the message 
"Three SSH login failures, first user is root" is mailed to root@localhost.
.PP
In order to use semicolons inside a non-constant parameter, 
the parameter must be enclosed in parentheses (the outermost set of
parentheses will be removed by SEC during configuration file parsing).
For example, the following action list consists of 
.I delete
and
.I shellcmd
actions:
.PP
action=delete MYCONTEXT; shellcmd (rm /tmp/sec1.tmp; rm /tmp/sec2.tmp)
.PP
The
.I delete
action deletes the context
.BR MYCONTEXT ,
while the
.I shellcmd
action executes the command line 
.IR "rm /tmp/sec1.tmp; rm /tmp/sec2.tmp" .
Since the command line contains a semicolon, it has been enclosed in
parentheses, since otherwise the semicolon would be mistakenly considered
a separator between two actions.
.PP
Apart from match variables, SEC supports 
.I action list variables
in action lists which facilitate data sharing between actions and Perl 
integration. Each action list variable has a name which must begin with 
a letter and consist of letters, digits and underscores. Names of built-in 
variables usually start with a dot character (.), so that they can be 
distinguished from user defined variables. In order to refer 
to an action list variable, its name must be prefixed by a percent sign (%). 
Unlike match variables, action list variables can only be used in 
action lists and they are substituted with their values immediately before 
the action list execution. Also, action list variables continue to exist
after the current action list has been executed and can be employed in
action lists of other rules.
.PP
The following action list variables are predefined by SEC:
.TP
.I %s 
operation description string (the value of the
.I desc
field after match variables have been substituted with their values).
Note that for the
.I action2
field of Pair and PairWithWindow rules, the %s variable is set by evaluating
the
.I desc2
field of the rule.
.TP
.I %t 
the time in human-readable format, as returned by the Perl
.BR localtime ()
function in the Perl scalar context (e.g., Fri Feb 19 17:54:18 2016).
.TP
.I %u 
the time in seconds since Epoch, as returned by the
.BR time (2)
system call.
.TP
.I %.sec 
number of seconds after the minute, in the range 00-59 
(the value consists of two digits and is zero padded on the left).
.TP
.I %.min 
number of minutes after the hour, in the range 00-59 
(the value consists of two digits and is zero padded on the left).
.TP
.I %.hour 
number of hours past midnight, in the range 00-23 
(the value consists of two digits and is zero padded on the left).
.TP
.I %.hmsstr 
the time in HH:MM:SS format (hours, minutes and seconds separated by colons, 
e.g., 09:32:04 or 18:06:02).
.TP
.I %.mday 
day of the month, in the range 01-31 
(the value consists of two digits and is zero padded on the left).
.TP
.I %.mdaystr 
day of the month as a string
(the value consists of two characters and is space padded on the left, 
e.g., " 1", " 4", " 9", or "25").
.TP
.I %.mon 
month, in the range 01-12 
(the value consists of two digits and is zero padded on the left).
.TP
.I %.monstr 
abbreviated name of the month according to the current locale, 
as returned by the %b specification of the 
.BR strftime (3)
library call
(e.g., Jan, May, or Sep).
.TP
.I %.year 
year (e.g., 1998 or 2016).
.TP
.I %.wday 
day of the week, in the range 0-6 (0 denotes Sunday).
.TP 
.I %.wdaystr 
abbreviated name of the day of the week according to the current locale, 
as returned by the %a specification of the
.BR strftime (3)
library call
(e.g., Mon, Wed, or Sat).
.TP
.I %.tzname 
name of the timezone according to the current locale,
as returned by the %Z specification of the
.BR strftime (3)
library call
(e.g., UTC or EET).
.TP
.I %.tzoff 
timezone offset from UTC, as returned by the %z specification of the
.BR strftime (3)
library call
(e.g., -0500 or +0200).
.TP
.I %.tzoff2 
timezone offset from UTC in +hh:mm/-hh:mm format (e.g., -05:00 or +02:00), 
provided that the %z specification of the
.BR strftime (3)
library call returns the value in +hhmm/-hhmm format (if the value
does not follow this format, %.tzoff2 is set to an empty string).
.TP
.I %.nl 
newline character.
.TP
.I %.cr 
carriage return character.
.TP
.I %.tab 
tabulation character.
.TP
.I %.sp
space character.
.TP
.I %.chr0, ..., %.chr255
ASCII 0..255 characters (e.g., %.chr7 is bell and %.chr12 is form feed 
character, whereas the sequence %.chr195%.chr132 is A-umlaut character
in UTF-8 encoding).
.PP
For example, the following action list assigns the current time in 
human-readable format and the string "This is a test event" to 
the %text action list variable, and mails the value of %text to
root@localhost:
.PP
action=assign %text %t: This is a test event; \\
       pipe '%text' /bin/mail root@localhost
.PP
If the action list is executed at Nov 19 10:58:51 2015, the
.I assign
action sets the %text action list variable to the string
"Thu Nov 19 10:58:51 2015: This is a test event", while the
.I pipe
action mails this string to root@localhost.
Note that unlike match variables, action list variables have a global scope,
and accessing the value of the %text variable in action lists of other rules 
will thus yield the string "Thu Nov 19 10:58:51 2015: This is a test event" 
(until another value is assigned to %text).
.PP
In order to disambiguate the variable from the following text, the variable 
name must be enclosed in braces. For example, the following action 
.PP
action=write - %{.year}-%{.mon}-%{.mday}T%{.hmsstr}%{.tzoff2}
.PP
writes a timestamp in ISO 8601 format to standard output, e.g.,
2016-02-24T07:34:01+02:00 (replacing %{.mday} with %.mday in the above action 
would mistakenly create a reference to %.mdayT variable).
.PP
When action list variables are substituted with their values, each 
sequence "%%" is interpreted as a literal percent sign (%) which allows 
for masking the variables. For example, the string "s%%t" becomes "s%t" 
after substitution, not "s%<timestamp>". 
.PP
However, note that if %-prefixed match variables are supported for the
.I action2
field of the Pair or PairWithWindow rule, the sequence "%%%" must be used in
.I action2
for masking a variable, since the string goes through *two* variable 
substitution rounds (first for %-prefixed match variables and then for action 
list variables, e.g., the string "s%%%t" first becomes "s%%t" and
finally "s%t").
.PP
Whenever a rule field goes through several substitution rounds, the $
or % characters are masked inside values substituted during earlier rounds,
in order to avoid unwanted side effects during later rounds.
.PP
If the action list variable has not been set,
it is substituted with an empty string (i.e., a zero-width string).
Thus the string "Value of A is: %a" becomes "Value of A is: " after
substitution if the variable %a is unset.
(Note that prior to SEC-2.6, unset variables were *not* substituted.)
.PP
Finally, the values are substituted as strings, therefore values of other 
types (e.g., references) lose their original meaning, unless explicitly noted 
otherwise (e.g., if a Perl function reference is stored to an action list 
variable, the function can later be invoked through this variable with the
.I call
action).
.PP
SEC supports the following actions (optional parameters are enclosed
in square brackets):
.TP 
.I none
No action.
.TP 
.I logonly [<string>]
Message <string> is logged to destinations given with the
.B \-\-log
and
.B \-\-syslog
options. The level of the log message is set to 4 (see the
.B \-\-debug
option for more information on log message levels). Default value
for <string> is %s. For example, consider the following action list definition:
.sp
action=logonly This is a test
.sp
The above 
.I logonly
action logs the message "This is a test" with level 4.
.TP 
.I write <filename> [<string>]
String <string> with a terminating newline is written to the file 
<filename> (<filename> may not contain whitespace). File may be a regular 
file, named pipe, or standard output (denoted by
.BR \- ).
If the file is a regular file, <string> is appended to the end of the file. 
If the file does not exist, it is created as a regular file before writing.
Note that the file will not be closed after the action completes, and
the following 
.I write
actions will access an already open file. 
However, several signals cause the file to be closed and reopened, and for
rotating files created with
.I write
action, the
.B SIGUSR2
signal can be used (see SIGNALS section for more information).
Default value for <string> is %s.
For example, consider the following action list definition:
.sp
action=write /var/log/test.log %t $0
.sp
The above
.I write
action prepends human-readable timestamp and separating space character to 
the value of the $0 match variable, and the resulting string is appended to file 
/var/log/test.log with terminating newline.
.TP
.I writen <filename> [<string>]
Similar to the
.I write
action, except that the string <string> is written without a terminating 
newline. Note that
.I write
and
.I writen
actions share the same filehandle for accessing the file.
For example, consider the following action list definition:
.sp
action=writen - ab; writen - c; writen - %.nl
.sp
The above action list writes the string "abc<NEWLINE>" to standard output,
and is thus identical to
.I write - abc
(and also to
.IR "writen - abc%.nl" ).
.TP 
.I closef <filename>
Close the file <filename> that has been previously opened by the
.I write
or
.I writen
action (<filename> may not contain whitespace).
.TP
.I owritecl <filename> [<string>]
Similar to the
.I write 
action, except that the file <filename> is opened and closed at each write. 
Also, the string <string> is written without a terminating newline. 
If the file has already been opened by a previous
.I write
action, 
.I owritecl
does not use existing filehandle, but opens and closes the file separately.
For example, consider the following action list definition:
.sp
action=owritecl /var/log/test-%{.year}%{.mon}%{.mday} $0%{.nl}
.sp
The above
.I owritecl
action appends the value of the $0 match variable with terminating newline to file 
/var/log/test-YYYYMMDD, where YYYYMMDD reflects the current date (e.g., if the current 
date is April 1 2018, the file is /var/log/test-20180401). Since the file is closed
after each write, the old file will not be left open when date changes.
.TP 
.I udgram <filename> [<string>]
String <string> is written to the UNIX datagram socket <filename> 
(<filename> may not contain whitespace). 
Note that the socket will not be closed after the action completes, and
the following 
.I udgram
actions will access an already open socket. 
However, several signals cause the socket to be closed and reopened
(see SIGNALS section for more information).
Default value for <string> is %s.
For example, consider the following action list definition:
.sp
action=udgram /dev/log <30>%.monstr %.mdaystr %.hmsstr sec: This is a test
.sp
The above
.I udgram
action sends a syslog message to local syslog daemon via /dev/log socket, where 
message priority is 30 (corresponds to the "daemon" facility and "info" level), 
syslog tag is "sec" and message text is "This is a test". Note that message substring
"%.monstr %.mdaystr %.hmsstr" evaluates to timestamp in BSD syslog format
(e.g., Mar 31 15:36:07).
.TP 
.I closeudgr <filename>
Close the UNIX datagram socket <filename> that has been previously opened by the
.I udgram
action (<filename> may not contain whitespace).
.TP 
.I ustream <filename> [<string>]
String <string> is written to the UNIX stream socket <filename> 
(<filename> may not contain whitespace).
Note that the socket will not be closed after the action completes, and
the following 
.I ustream
actions will access an already open socket.
However, several signals cause the socket to be closed and reopened
(see SIGNALS section for more information).
Default value for <string> is %s.
.TP 
.I closeustr <filename>
Close the UNIX stream socket <filename> that has been previously opened by the
.I ustream
action (<filename> may not contain whitespace).
.TP 
.I udpsock <host>:<port> [<string>]
String <string> is sent to the UDP port <port> of the host <host>.
Note that the UDP socket which is used for communication will not be closed 
after the action completes, and the following 
.I udpsock
actions for the same remote peer will use an already existing socket.
However, several signals cause the socket to be closed and recreated
(see SIGNALS section for more information).
Default value for <string> is %s.
For example, consider the following action list definition:
.sp
action=udpsock mysrv:514 <13>%.monstr %.mdaystr %.hmsstr myhost test: $0
.sp
The above
.I udpsock
action sends a BSD syslog message to port 514/udp of remote syslog server mysrv, 
where message priority is 13 (corresponds to the "user" facility and "notice" level), 
name of the local host is "myhost", syslog tag is "test" and message text is 
the value if the $0 match variable.
.TP 
.I closeudp <host>:<port>
Close the UDP socket for peer <host>:<port> that has been previously opened 
by the
.I udpsock
action.
.TP 
.I tcpsock <host>:<port> [<string>]
String <string> is sent to the TCP port <port> of the host <host>.
The timeout value given with the
.B \-\-socket\-timeout
option determines for how many seconds SEC will attempt to establish 
a connection to the remote peer. If the connection establishment does
not succeed immediately, the
.I tcpsock
action buffers <string> in memory for later sending to the remote peer.
Note that the relevant TCP socket will not be closed after <string>
has been transmitted, and the following 
.I tcpsock
actions for the same peer will use an already existing socket.
However, several signals cause the socket to be closed and recreated
(see SIGNALS section for more information).
Default value for <string> is %s.
For example, consider the following action list definition:
.sp
action=tcpsock grsrv:2003 ssh.login.failures %{num} %{u}%{.nl}
.sp
The above
.I tcpsock
action sends the value of the action list variable %{num} to port 2003/tcp
of the Graphite server grsrv, so that the value is recorded under metric path
ssh.login.failures. Note that the %{u} action list variable evaluates
to current time in seconds since Epoch and is used for setting the timestamp
for recorded value.
.TP 
.I closetcp <host>:<port>
Close the TCP socket for peer <host>:<port> that has been previously opened 
by the
.I tcpsock
action.
.TP 
.I shellcmd <cmdline>
Fork a process for executing command line <cmdline>. 
If <cmdline> contains shell metacharacters, <cmdline> is parsed by shell. 
If the
.B \-\-quoting
option was specified and <cmdline> contains %s variables, the value of %s
is quoted with single quotes before substituting it into <cmdline>; 
if the value of %s contains single quotes, they are masked with backslashes
(e.g., abc is converted to 'abc' and aa'bb is converted to 'aa'\\''bb').
For additional information, see CHILD PROCESSES section.
For example, consider the following action list definition:
.sp
action=shellcmd (cat /tmp/report | mail root; rm -f /tmp/report); \\
       logonly Report sent to user root
.sp
The
.I shellcmd
action of this action list executes the command line 
.sp
cat /tmp/report | mail root; rm -f /tmp/report
.sp
and the
.I logonly
action logs the message "Report sent to user root". 
Since the command line contains a semicolon which is used for separating
.I shellcmd
and
.I logonly
actions, the command line is enclosed in parentheses.
.TP
.I spawn <cmdline>
Similar to the
.I shellcmd
action, except that each line from the standard output of <cmdline> 
becomes a synthetic event and will be treated like a line from input file 
(see the
.I event
action for more information). If the
.B \-\-intcontexts
command line option is given, internal context _INTERNAL_EVENT is set
up before each synthetic event is processed (see INTERNAL EVENTS AND
CONTEXTS section for more information).
For example, consider the following action list definition:
.sp
action=spawn (cat /tmp/events; rm -f /tmp/events)
.sp
The above
.I spawn
action will generate synthetic events from all lines in file /tmp/events
and remove the file. Since the command line contains a semicolon which
is used for separating actions, the command line is enclosed in parentheses.
.TP 
.I cspawn <name> <cmdline>
Similar to the
.I spawn
action, except that if the
.B \-\-intcontexts
command line option is given, internal context <name> is set up for each 
synthetic event. 
.TP
.I cmdexec <cmdline>
Fork a process for executing command line <cmdline>. 
Unlike
.I shellcmd
action, <cmdline> is not parsed by shell, but split into arguments by 
using whitespace as a separator, and passed to 
.BR execvp (3) 
for execution. Note that splitting into arguments is done when
.I cmdexec
action is loaded from the configuration file and parsed, not at runtime 
(e.g., if <cmdline> is
.IR "/usr/local/bin/mytool $1 $2" ,
the values of $1 and $2 variables are regarded as single arguments even if
the values contain whitespace).
For additional information, see CHILD PROCESSES section.
For example, consider the following action list definition:
.sp
action=cmdexec rm /tmp/report*
.sp
The above 
.I cmdexec
action will remove the file /tmp/report* without treating * as a file
pattern character that matches any string.
.TP
.I spawnexec <cmdline>
Similar to the
.I cmdexec
action, except that each line from the standard output of <cmdline>
becomes a synthetic event and will be treated like a line from input file
(see the
.I event
action for more information). If the
.B \-\-intcontexts
command line option is given, internal context _INTERNAL_EVENT is set
up before each synthetic event is processed (see INTERNAL EVENTS AND
CONTEXTS section for more information).
.TP
.I cspawnexec <name> <cmdline>
Similar to the
.I spawnexec
action, except that if the
.B \-\-intcontexts
command line option is given, internal context <name> is set up for each 
synthetic event. 
.TP 
.I pipe '[<string>]' [<cmdline>]
Fork a process for executing command line <cmdline>. 
If <cmdline> contains shell metacharacters, <cmdline> is parsed by shell. 
The string <string> 
with a terminating newline is written to the standard input of <cmdline> 
(single quotes are used for disambiguating <string> from <cmdline>).
If <string> contains semicolons, <string> must be enclosed in parentheses
(e.g.,
.IR "pipe '($1;$2)' /bin/cat" ).
Default value for <string> is %s.
If <cmdline> is omitted, <string> is written to standard output.
For additional information, see CHILD PROCESSES section.
For example, consider the following action list definition:
.sp
action=pipe 'Offending activities from host $1' /bin/mail root@localhost
.sp
The above
.I pipe
action writes the line "Offending activities from host <hostname>"
to the standard input of the
.I /bin/mail root@localhost
command which sends this line to root@localhost via e-mail
(<hostname> is the value of the $1 match variable). 
.TP
.I pipeexec '[<string>]' [<cmdline>]
Similar to the
.I pipe
action, except <cmdline> is not parsed by shell, but split into arguments by
using whitespace as a separator, and passed to 
.BR execvp (3) 
for execution. Note that splitting into arguments is done when
.I pipeexec
action is loaded from the configuration file and parsed, not at runtime 
(e.g., if <cmdline> is
.IR "/usr/local/bin/mytool $1 $2" ,
the values of $1 and $2 variables are regarded as single arguments even if
the values contain whitespace).
For example, consider the following action list definition:
.sp
action=pipeexec 'Offending activities from host $1' \\
                /bin/mail -s SEC%{.sp}alert $2
.sp
The above
.I pipeexec
action writes the line "Offending activities from host <hostname>"
to the standard input of the
.I /bin/mail -s <subject> <user>
command which sends this line to <user> via e-mail with subject <subject>
(<hostname> is the value of the $1 match variable, while <user> is the value
of the $2 match variable). Note that since <subject> is defined as
SEC%{.sp}alert and does not contain whitespace, it is treated as a single
argument for the -s flag of the /bin/mail command. However, since <subject>
contains the %.sp action list variable, the string "SEC alert" will be used
for the e-mail subject at runtime. Also, if the value of the $2 match variable 
contains shell metacharacters, they will not be interpreted by the shell.
.TP 
.I create [<name> [<time> [<action list>] ] ]
Create a context with the name <name>, lifetime of <time> seconds, and 
empty event store. The <name> parameter may not contain whitespace and defaults
to %s. The <time> parameter must evaluate to an unsigned integer at runtime.
Specifying 0 for <time> or omitting the value means infinite lifetime.
If <action list> is given, it will be executed when the context expires.
If <action list> contains several actions, the list must be enclosed in
parentheses. In <action list>, the internal context name _THIS may be used
for referring to the current context (see INTERNAL EVENTS AND CONTEXTS
section for a detailed discussion).
If an already existing context is recreated with
.IR create , 
its remaining lifetime is set to <time> seconds, its action list is
reinitialized, and its event store is emptied.
For example, consider the following action list definition:
.sp
action=write /var/log/test.log $0; create TIMER 3600 \\
       ( logonly Closing /var/log/test.log; closef /var/log/test.log )
.sp
The
.I write
action from the above action list appends the value of the $0 match variable
to file /var/log/test.log, while the
.I create
action creates the context TIMER which will exist for 3600 seconds. Since this
context is recreated at each write, the context can expire only if the action
list has not been executed for more than 3600 seconds (i.e., the action list has 
last updated the file more than 1 hour ago). If that is the case, the action list
.sp
logonly Closing /var/log/test.log; closef /var/log/test.log
.sp
is executed which logs the message "Closing /var/log/test.log" with the
.I logonly
action and closes /var/log/test.log with the
.I closef
action. When the execution of this action list is complete, the TIMER context
is deleted.
.TP 
.I delete [<name>]
Delete the context <name>. The <name> parameter may not contain whitespace
and defaults to %s.
.TP 
.I obsolete [<name>]
Similar to the
.I delete 
action, except that the action list of the context <name> (if present)  
is executed before deletion.
.TP 
.I set <name> <time> [<action list>]
Change settings for the context <name>. The creation time of the context
is set to the current time, and the lifetime of the context is set to <time> 
seconds.
If the <action list> parameter is given, the context action list is set 
to <action list>, otherwise the context action list is not changed. 
The <name> parameter may not contain whitespace and defaults to %s.
The <time> parameter must evaluate to an unsigned integer or hyphen (-) 
at runtime.
Specifying 0 for <time> means infinite lifetime.
If <time> equals to -, the creation time and lifetime of the context are 
not changed.
If <action list> contains several actions, the list must be enclosed in
parentheses. In <action list>, the internal context name _THIS may be used
for referring to the current context (see INTERNAL EVENTS AND CONTEXTS
section for a detailed discussion).
For example, consider the following action list definition:
.sp
action=set C_$1 30 ( logonly Context C_$1 has expired )
.sp
The above
.I set
action sets the context C_<suffix> to expire after 30 seconds with a log
message about expiration (<suffix> is the value of the $1 match variable).
.TP 
.I alias <name> [<alias>]
Create an alias name <alias> for the context <name>. After creation,
both <alias> and <name> will point to the same context data structure,
and can thus be used interchangeably for referring to the context.
The <name> and <alias> parameters may not contain whitespace, and <alias>
defaults to %s.
If the context <name> does not exist, the alias name is not created.
If the
.I delete
action is called for one of the context names, the context data structure is
destroyed, and all context names (which are now pointers to unallocated
memory) cease to exist. Also note that when the 
context expires, its action list is executed only once, 
no matter how many names the context has.
.TP 
.I unalias [<alias>]
Drop an existing context name <alias>, so that it can no longer be used for
referring to the given context. The <alias> parameter may not contain 
whitespace and defaults to %s. 
If the name <alias> is the last reference to the context, the 
.I unalias
action is identical to
.IR delete .
.TP 
.I add <name> [<string>]
String <string> is appended to the end of the event store of the context 
<name>. 
The <name> parameter may not contain whitespace, and the <string> parameter
defaults to %s.
If the context <name> does not exist, the context is created with
an infinite lifetime, empty action list and empty event store (as with
.IR "create <name>" )
before adding the string to event store. 
If <string> is a multi-line string (i.e., it contains newlines), it is
split into lines, and each line is appended to the event store separately.
For example, consider the following action list definition:
.sp
action=add EVENTS This is a test; add EVENTS This is a test2
.sp
After the execution of this action list, the last two strings in the event
store of the EVENTS context are "This is a test" and "This is a test2"
(in that order).
.TP 
.I prepend <name> [<string>]
Similar to the
.I add 
action, except that the string <string> is prepended to the beginning
of the event store of context <name>. 
For example, consider the following action list definition:
.sp
action=prepend EVENTS This is a test; prepend EVENTS This is a test2
.sp
After the execution of this action list, the first two strings in the event
store of the EVENTS context are "This is a test2" and "This is a test"
(in that order).
.TP 
.I fill <name> [<string>]
Similar to the
.I add 
action, except that the event store of the context <name> is emptied 
before <string> is added.
.TP 
.I report <name> [<cmdline>]
Fork a process for executing command line <cmdline>. 
If <cmdline> contains shell metacharacters, <cmdline> is parsed by shell. 
Also, write strings from the event store of the context <name> to the standard 
input of <cmdline>.
Strings are written in the order they appear in the event store, with
a terminating newline appended to each string.
If the context <name> does not exist or its event store is empty, <cmdline>
is not executed.
The <name> parameter may not contain whitespace, and if <cmdline> is omitted,
strings are written to standard output.
For additional information, see CHILD PROCESSES section.
For example, consider the following action list definition:
.sp
action=create PID_$1 60 ( report PID_$1 /bin/mail root@localhost ); \\
       add PID_$1 Beginning of the report
.sp
The above action list creates the context PID_<suffix> with the lifetime 
of 60 seconds and sets the first string in the context event store to
"Beginning of the report" (<suffix> is the value of the $1 match variable).
When the context expires, all strings from the event store will be mailed
to root@localhost.
.TP 
.I reportexec <name> [<cmdline>]
Similar to the
.I report
action, except <cmdline> is not parsed by shell, but split into arguments by
using whitespace as a separator, and passed to 
.BR execvp (3) 
for execution. Note that splitting into arguments is done when
.I reportexec
action is loaded from the configuration file and parsed, not at runtime 
(e.g., if <cmdline> is
.IR "/usr/local/bin/mytool $1 $2" ,
the values of $1 and $2 variables are regarded as single arguments even if
the values contain whitespace).
.TP
.I copy <name> %<var>
Strings s1,...,sn from the event store of the context <name> are joined
into a multi-line string "s1<NEWLINE>...<NEWLINE>sn", and this string is
assigned to the action list variable %<var>.
If the context <name> does not exist, the value of %<var> does not change.
.TP 
.I empty <name> [%<var>]
Similar to the
.I copy
action, except that the event store of the context <name> will be emptied 
after the assignment. If %<var> is omitted, the content of the event store
is dropped without an assignment.
.TP 
.I pop <name> %<var>
Remove the last string from the event store of context <name>, and assign
it to the action list variable %<var>. If the event store is empty, %<var> 
is set to empty string.
If the context <name> does not exist, the value of %<var> does not change.
.TP 
.I shift <name> %<var>
Remove the first string from the event store of context <name>, and assign
it to the action list variable %<var>. If the event store is empty, %<var> 
is set to empty string.
If the context <name> does not exist, the value of %<var> does not change.
.TP 
.I exists %<var> <name>
If the context <name> exists, set the action list variable %<var> to 1, 
otherwise set %<var> to 0.
.TP 
.I getsize %<var> <name>
Find the number of strings in the event store of context <name>, and
assign this number to the action list variable %<var>.
If the context <name> does not exist, %<var> is set to Perl undefined value.
For example, consider the following action list definition:
.sp
action=fill EVENTS Event1; add EVENTS Event2; add EVENTS Event3; \\
       pop EVENTS %temp1; shift EVENTS %temp2; getsize %size EVENTS
.sp
This action list sets the %temp1 action list variable to Event3, %temp2 action 
list variable to Event1, and %size action list variable to 1.
.TP 
.I getaliases %<var> <name>
Find all alias names for context <name>, join the names into a multi-line 
string "alias1<NEWLINE>...<NEWLINE>aliasn", and assign this string to
the action list variable %<var>.
If the context <name> does not exist, the value of %<var> does not change.
.TP 
.I getltime %<var> <name>
Find the lifetime of context <name>, and assign this number to the action 
list variable %<var>.
If the context <name> does not exist, the value of %<var> does not change.
For example, consider the following action list definition:
.sp
action=create TEST 10 ( getltime %time TEST; \\
       logonly Context TEST with %time second lifetime has expired )
.sp
The above
.I create
action configures the context TEST to log its lifetime when it expires.
.TP
.I setltime <name> [<time>]
Set the lifetime of context <name> to <time>. 
Specifying 0 for <time> or omitting the value means infinite lifetime.
Note that unlike the
.I set
action, 
.I setltime
does not adjust the context creation time. For example, if context TEST
has been created at 12:01:00 with the lifetime of 60 seconds, then after invoking
.I setltime TEST 30 
at 12:01:20 the context would exist until 12:01:30, while invoking
.I setltime TEST 10
would immediately expire the context.
.TP 
.I getctime %<var> <name>
Find the creation time of context <name>, and assign this timestamp to the action 
list variable %<var>.
The value assigned to %<var> is measured in seconds since Epoch 
(as reported by the
.BR time (2)
system call).
If the context <name> does not exist, the value of %<var> does not change.
.TP 
.I setctime <time> <name>
Set the creation time of context <name> to <time>. 
The <time> parameter must evaluate to seconds since Epoch (as reported by the
.BR time (2)
system call), and must reflect a time moment between the previous creation
time and the current time (both endpoints included).
For example, if context TEST has been created at 12:43:00 with the lifetime 
of 60 seconds, then after invoking
.I setctime %u TEST 
at 12:43:25 the context would exist until 12:44:25 (the %u action list
variable evaluates to current time in seconds since Epoch).
.TP 
.I event [<time>] [<string>]
After <time> seconds, create a synthetic event <string>. 
If <string> is a multi-line string (i.e., it contains newlines), it is
split into lines, and from each line a separate synthetic event is created.
SEC will treat each synthetic event like a line from an input file -- 
the event will be matched against rules and it might trigger further actions.
If the
.B \-\-intcontexts 
command line option is given, internal context _INTERNAL_EVENT is set up
for synthetic event(s) (see INTERNAL EVENTS AND CONTEXTS section for more 
information).
The <time> parameter is an integer constant. Specifying 0 for <time> or
omitting the value means "now". Default value for <string> is %s.
For example, consider the following action list definition:
.sp
action=copy EVENTS %events; event %events
.sp
The above action list will create a synthetic event from each string 
in the event store of the EVENTS context.
.TP 
.I tevent <time> [<string>]
Similar to the
.I event
action, except that the <time> parameter may contain variables and must 
evaluate to an unsigned integer at runtime.
.TP 
.I cevent <name> <time> [<string>]
Similar to the
.I tevent
action, except that if the
.B \-\-intcontexts 
command line option is given, internal context <name> is set up for
synthetic event(s).
.TP 
.I reset [<offset>] [<string>]
Terminate event correlation operation(s) with the operation description string
<string>. Note that the
.I reset
action works only for operations started from the same configuration file.
The <offset> parameter is used to refer to a specific rule in the 
configuration file. If <offset> is given, the operation started by the
given rule is terminated (if it exists).
If <offset> is an unsigned integer N, it refers to the N-th rule in the 
configuration file. If <offset> is 0, it refers to the current rule. If
<offset> begins with the plus (+) or minus (-) sign, it specifies an offset
from the current rule (e.g., -1 denotes the previous and +1 the next rule).
Note that since Options rules are only processed when configuration files
are loaded and they are not applied at runtime, Options rules are excluded 
when calculating <offset>.
If <offset> is not given, SEC checks for each rule from the current
configuration file if an operation with <string> has been started by this 
rule, and the operation is terminated if it exists.
Default value for <string> is %s.
For additional information, see EVENT CORRELATION OPERATIONS section.
For example, consider the following action list definition:
.sp
action=reset -1 Ten login failures observed from $1; reset 0
.sp
If the above action list is executed by an event correlation operation,
the first
.I reset
action will terminate another event correlation operation which has been started 
by the previous rule and has the operation description string "Ten login failures 
observed from <host>" (<host> is the value of the $1 match variable). The second
.I reset
action will terminate the calling operation itself.
.TP 
.I getwpos %<var> <offset> [<string>]
Find the beginning of the event correlation window for an event correlation 
operation, and set the action list variable %<var> to this timestamp. 
The value assigned to %<var> is measured in seconds since Epoch 
(as reported by the
.BR time (2)
system call). As with the
.I reset
action, the event correlation operation is identified by the operation 
description string <string> and the rule offset <offset>. 
If the operation does not exist, the value of %<var> does not change.
Default value for <string> is %s.
For additional information, see EVENT CORRELATION OPERATIONS section.
For example, consider the following action list definition:
.sp
action=getwpos %pos -1 Ten login failures observed from $1
.sp
The above
.I getwpos
action will find the beginning of the event correlation window for an event
correlation operation which has been started by the previous rule and has 
the operation description string "Ten login failures observed from <host>" 
(<host> is the value of the $1 match variable). If the event correlation
window begins at April 6 08:03:53 2018 UTC, the value 1523001833 will be
assigned to the %pos action list variable.
.TP 
.I setwpos <time> <offset> [<string>]
Set the beginning of the event correlation window to <time> for an event
correlation operation (if it exists). The <time> parameter must evaluate to 
seconds since Epoch (as reported by the
.BR time (2)
system call), and must reflect a time moment between the previous window
position and the current time (both endpoints included). As with the
.I reset
action, the event correlation operation is identified by the operation 
description string <string> and the rule offset <offset>.
Default value for <string> is %s.
For additional information, see EVENT CORRELATION OPERATIONS section.
.TP 
.I assign %<var> [<string>]
Assign string <string> to the action list variable %<var>. 
Default value for <string> is %s.
.TP
.I assignsq %<var> [<string>]
Similar to the
.I assign
action, except that <string> is quoted with single quotes before assigning
it to %<var>. If <string> contains single quotes, they are masked with
backslashes (e.g., if the match variable $1 holds the value 
abc'123'xyz, the action
.I assignsq %myvar $1
assigns the value 'abc'\\''123'\\''xyz' to the action list variable %myvar).
This action is useful for disabling shell interpretation 
for the values of action list variables that appear in command lines executed 
by SEC.
Default value for <string> is %s.
.TP 
.I free %<var>
Unset the action list variable %<var>. 
.TP 
.I eval %<var> <code>
The parameter <code> is a Perl miniprogram that is compiled and executed
by calling the Perl 
.BR eval ()
function in the Perl list context. 
If the miniprogram returns a single value, 
it is assigned to the action list variable %<var>. If the miniprogram 
returns several values s1,...,sn, they are joined into a multi-line string
"s1<NEWLINE>...<NEWLINE>sn", and this string is assigned to %<var>.
If no value is returned, %<var> is set to Perl undefined value. If
.BR eval ()
fails, the value of %<var> does not change.
Since most Perl programs contain semicolons which are also employed by SEC
as action separators, it is recommended to enclose the <code> parameter in 
parentheses, in order to mask the semicolons in <code>.
For additional information, see PERL INTEGRATION section.
For example, consider the following action list definition:
.sp
action=assign %div Division error; eval %div ( $1 / $2 )
.sp
The 
.I assign
action sets the %div action list variable to the string "Division error", 
while the 
.I eval
action substitutes the values of $1 and $2 match variables into the string
"$1 / $2". Resulting string is treated as Perl code which is first compiled 
and then executed. For instance, if the values of $1 and $2 are 12 and 4,  
respectively, the following Perl code is compiled: 12 / 4. Since executing 
this code yields 3, the 
.I eval
action assigns this value to the %div action list variable. 
Also, if $2 has no value or its value is 0, resulting code leads to compilation 
or execution error, and %div retains its previous value "Division error".
.TP 
.I call %<var> %<ref> [<paramlist>]
Call the precompiled Perl function referenced by the action list variable 
%<ref>, and assign the result to the action list variable %<var>.
The %<ref> parameter must be a code reference that has been previously
created with the
.I eval
action. The <paramlist> parameter (if given) is a string which specifies 
parameters for the function. The parameters must be separated by whitespace 
in the <paramlist> string.
If the function returns a single value, it is assigned to %<var>.
If the function returns several values s1,...,sn, they are joined into 
a multi-line string "s1<NEWLINE>...<NEWLINE>sn", and this string is assigned 
to %<var>. If no value is returned, %<var> is set to Perl undefined value. 
If the function encounters a fatal runtime error or %<ref> is not a code 
reference, the value of %<var> does not change.
For additional information, see PERL INTEGRATION section.
For example, consider the following action list definition:
.sp
action=eval %func ( sub { return $_[0] + $_[1] } ); \\
       call %sum %func $1 $2
.sp
Since the Perl code provided to
.I eval
action is a definition of an anonymous function, its compilation yields
a code reference which gets assigned to the %func action list variable
(the function returns the sum of its two input parameters).
The
.I call
action will invoke previously compiled function, using the values of $1 and $2 
match variables as function parameters, and assigning function return value
to the %sum action list variable. Therefore, if the values of $1 and $2 are
2 and 3, respectively, %sum is set to 5.
.TP 
.I lcall %<var> [<paramlist>] \-> <code>
.TP
.I lcall %<var> [<paramlist>] :> <code>
Call the precompiled Perl function <code> and assign the result to the action
list variable %<var>.
The <code> parameter must be a valid Perl anonymous function definition that 
is compiled at SEC startup with the Perl
.BR eval ()
function, and
.BR eval ()
must return a code reference.
The <paramlist> parameter (if given) is a string which specifies 
parameters for the function. The parameters must be separated by whitespace 
in the <paramlist> string.
If <paramlist> is followed by -> operator, parameters are passed to function 
as Perl scalar values.
If <paramlist> is followed by :> operator, it is assumed that each parameter
is a name of an entry in the pattern match cache. If an entry with the given name
does not exist, Perl undefined value is passed to the function. If an entry with
the given name exists, a reference to the entry is passed to the function.
Internally, each pattern match cache entry is implemented as a Perl hash which 
contains all match variables for the given entry.
If the function returns a single value, it is assigned to %<var>.
If the function returns several values s1,...,sn, they are joined into 
a multi-line string "s1<NEWLINE>...<NEWLINE>sn", and this string is assigned 
to %<var>. If no value is returned, %<var> is set to Perl undefined value.
If the function encounters a fatal runtime error, 
the value of %<var> does not change.
Since most Perl functions contain semicolons which are also employed by SEC
as action separators, it is recommended to enclose the <code> parameter in 
parentheses, in order to mask the semicolons in <code>.
For additional information, see PERL INTEGRATION section.
For example, consider the following action list definition:
.sp
action=lcall %len $1 -> ( sub { return length($_[0]) } )
.sp
The above
.I lcall
action will take the value of the $1 match variable and find its length in characters,
assigning the length to the %len action list variable. Note that the function for
finding the length is compiled when SEC loads its configuration, and all invocations of 
.I lcall
will execute already compiled code. 
As another example, consider the following action list definition:
.sp
action=lcall %o SSH :> ( sub { $_[0]->{"failure"} = 1 } )
.sp
The above
.I lcall
action will assign 1 to the $+{failure} match variable that has been cached under
the SSH entry in the pattern match cache (variable will be created if it did not
exist previously).
.TP
.I rewrite <lnum> [<string>]
Replace last <lnum> lines in the input buffer with string <string>. If the
.B \-\-nojointbuf 
option was specified and the action is triggered by a matching event, 
the action modifies the buffer which holds this event. If the
.B \-\-nojointbuf 
option was specified and the action is triggered by the system clock 
(e.g., the action is executed from the Calendar rule), 
the action modifies the buffer which holds the last already processed event. 
With the
.B \-\-jointbuf 
option, the content of the joint input buffer is rewritten. The <lnum> 
parameter must evaluate to an unsigned integer at runtime. If <lnum> evaluates 
to 0, <lnum> is reset to the number of lines in <string>.
If the value of <lnum> is greater than the buffer size N, <lnum> is reset to N. 
If <string> contains less than <lnum> lines, <string> will be padded with 
leading empty lines. If <string> contains more than <lnum> lines, 
only leading <lnum> lines from <string> are written into the buffer. 
Default value for <string> is %s. 
For additional information, see INPUT PROCESSING AND TIMING section.
.TP
.I addinput <filename> [<offset> [<name>] ]
File <filename> is added to the list of input files and opened, so that
processing starts from file offset <offset>. The <offset> parameter must
evaluate to unsigned integer or 
.B \-
(EOF) at runtime.
If <offset> is not specified, it defaults to
.B \- 
(i.e., processing starts from the end of file).
If opening the file fails (e.g., the file does not exist), it will stay in
the list of input files (e.g., with the
.B \-\-reopen\-timeout
command line option, SEC will attempt to reopen the file). 
The <name> parameter defines the internal context which should be used for
<filename> if the
.B \-\-intcontexts
command line option is given (if <name> is omitted but 
.B \-\-intcontexts
command line option is present, default internal context will be used).
See INTERNAL EVENTS AND CONTEXTS section for more information.
For example, consider the following action list definition:
.sp
action=addinput /var/log/test-%{.year}%{.mon}%{.mday} 0 TESTFILE
.sp
The above
.I addinput
action adds the file /var/log/test-YYYYMMDD to the list of input files,
where YYYYMMDD reflects the current date. The
.I addinput
action will also attempt to open the file, and if open succeeds,
file will be processed from the beginning. Also, the internal context
TESTFILE will be used for all events read from the file.
.TP
.I dropinput <filename>
File <filename> is dropped from the list of input files and closed 
(if currently open). Note that
.I dropinput
action can only be used for input files which have been previously set up with
.I addinput
action.
.TP
.I sigemul <signal>
Emulates the arrival of signal <signal> and triggers its handler.
The <signal> parameter must evaluate to one of the following strings:
HUP, ABRT, USR1, USR2, INT, or TERM. For example, the action
.I sigemul USR1
triggers the generation of SEC dump file. See the SIGNALS section for
detailed information on signals that are handled by SEC.
.TP
.I varset %<var> <entry>
If the pattern match cache entry <entry> exists, set the action list variable 
%<var> to 1, otherwise set %<var> to 0. For example, if pattern match cache
contains the entry with the name SSH but not the entry with the name NTP, 
the action
.I varset %ssh SSH
will set the %ssh action list variable to 1, while the action
.I varset %ntp NTP
will set the %ntp action list variable to 0.
.TP
.I if %<var> ( <action list> ) [ else ( <action list2> ) ]
If the action list variable %<var> evaluates true in the Perl boolean context
(i.e., it holds a defined value which is neither 0 nor empty string), execute 
the action list <action list>. If the second action list <action list2> is 
given with the optional else-statement, it is executed if %<var> either does 
not exist or evaluates false (i.e., %<var> holds 0, empty string or Perl 
undefined value).
For example, consider the following action list definition:
.sp
action=exists %present REPORT; if %present \\
         ( report REPORT /bin/mail root@localhost; delete REPORT ) \\
         else ( logonly Nothing to report )
.sp
If the REPORT context exists, its event store is mailed to root@localhost
and the context is deleted, otherwise the message "Nothing to report"
is logged.
.TP
.I while %<var> ( <action list> )
Execute the action list <action list> repeatedly as long as the action list 
variable %<var> evaluates true in the Perl boolean context
(i.e., it holds a defined value which is neither 0 nor empty string). 
For example, consider the following action list definition:
.sp
action=create REVERSE; getsize %n TEST; \\
       while %n ( pop TEST %e; add REVERSE %e; getsize %n TEST ); \\
       copy REVERSE %events; fill TEST %events
.sp
This action list reverses the order of strings in the event store of
the context TEST, using the context REVERSE as a temporary storage.
During each iteration of the while-loop, the last string in the event
store of TEST is removed with the
.I pop
action and appended to the event store of REVERSE with the
.I add 
action. The loop terminates when all strings have been removed from 
the event store of TEST (i.e., the 
.I getsize
action reports 0 for event store size). Finally, the event store of REVERSE
is assigned to the %events action list variable with the
.I copy
action, and the
.I fill
action is used for overwriting the event store of TEST with the value
of %events. 
.TP
.I break
If used inside a while-loop, terminates its execution; 
otherwise terminates the execution of the entire action list.
.TP
.I continue
If used inside a while-loop, starts the next iteration of the loop; 
otherwise terminates the execution of the entire action list.
.PP
.B Examples:
.PP
Follow the /var/log/trapd.log file and feed to SEC input all lines that are 
appended to the file:
.PP
action=spawn /bin/tail -f /var/log/trapd.log
.PP
Mail the timestamp and the value of the $0 variable to the local root:
.PP
action=pipe '%t: $0' /bin/mail -s "alert message" root@localhost
.PP
Add the value of the $0 variable to the event store of the context 
.BR "ftp_<the value of $1>" , 
and set the context to expire after 30 minutes. 
When the context expires, its event store will be mailed to the local root:
.PP
action=add ftp_$1 $0; \\
       set ftp_$1 1800 (report ftp_$1 /bin/mail root@localhost)
.PP
Create a subroutine for weeding out comment lines from the input list, and 
use this subroutine for removing comment lines from the event store of the 
context 
.BR C1 :
.PP
action=eval %funcptr ( sub { my(@buf) = split(/\\n/, $_[0]); \\
            my(@ret) = grep(!/^#/, @buf); return @ret; } ); \\
       copy C1 %in; call %out %funcptr %in; fill C1 %out
.PP
The following action list achieves the same goal as the previous action list
with 
.I while 
and 
.I if 
actions:
.PP
action=getsize %size C1; while %size ( shift C1 %event; \\
       lcall %nocomment %event -> ( sub { $_[0] !~ /^#/ } ); \\
       if %nocomment ( add C1 %event ); \\
       lcall %size %size -> ( sub { $_[0]-1; } ) )
.SH "PARSING ISSUES"
As already noted, SEC context expressions and action lists may contain
parentheses which are used for grouping and masking purposes. When SEC parses
its configuration, it checks whether parentheses in context expressions and
action lists are balanced (i.e., whether each parenthesis has a counterpart),
since unbalanced parentheses introduce ambiguity. This can cause SEC to reject
some legitimate constructs, e.g., 
.PP
action=eval %o (print ")";)
.PP
is considered an invalid action list (however, note that 
.br
action=eval %o (print "()";)
.br
would be passed by SEC, since now parentheses are balanced). 
In order to avoid such parsing errors, each parenthesis without
a counterpart must be masked with a backslash (the backslash will be removed 
by SEC during configuration file parsing). For example, the above action
could be written as
.PP
action=eval %o (print "\\)";)
.SH "RULE TYPES"
This section provides a detailed discussion of SEC rule types.
.SS "SINGLE RULE"
The Single rule supports the following fields.
Note that match variables may be used in
.IR context ,
.IR desc ,
and
.I action
fields.
.TP 
.I type
fixed to Single (value is case insensitive, so single or sIngLe can be
used instead).
.TP 
.IR continue " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive). 
.TP 
.I ptype
pattern type (value is case insensitive).
.TP 
.I pattern
pattern.
.TP 
.IR varmap " (optional)"
variable map.
.TP 
.IR context " (optional)"
context expression.
.TP 
.I desc
operation description string. 
.TP 
.I action
action list.
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B Single
rule immediately executes an action list when an event has matched the rule.
An event matches the rule if the pattern matches the event and the context
expression (if given) evaluates TRUE.
.PP
Note that the Single rule does not start event correlation operations, 
and the
.I desc
field is merely used for setting the %s action list variable.
.PP
.B Examples:
.PP
type=single
.br
continue=takenext
.br
ptype=regexp
.br
pattern=ftpd\\[(\\d+)\\]: \\S+ \\(ristov2.*FTP session opened
.br
desc=ftp session opened for ristov2 pid $1
.br
action=create ftp_$1
.PP 
type=single
.br
continue=takenext
.br
ptype=regexp
.br
pattern=ftpd\\[(\\d+)\\]:
.br
context=ftp_$1
.br
desc=ftp session event for ristov2 pid $1
.br
action=add ftp_$1 $0; set ftp_$1 1800 \\
         (report ftp_$1 /bin/mail root@localhost)
.PP 
type=single
.br
ptype=regexp
.br
pattern=ftpd\\[(\\d+)\\]: \\S+ \\(ristov2.*FTP session closed
.br
desc=ftp session closed for ristov2 pid $1
.br
action=report ftp_$1 /bin/mail root@localhost; \\
       delete ftp_$1
.PP
This ruleset is created for monitoring the ftpd log file.
The first rule creates the context 
.B ftp_<pid>
when someone connects from host ristov2 over FTP and establishes a new ftp
session (the session is identified by the PID of the process which has been
created for handling this session). The second rule adds all further
log file lines for the session <pid> to the event store of the context
.B ftp_<pid> 
(before adding a line, the rule checks if the context exists). After
adding a line, the rule extends context's lifetime for 30 minutes and sets 
the action list that will be executed when the context expires. The third rule 
mails collected log file lines to root@localhost when the session <pid> is 
closed. Collected lines will also be mailed when the session <pid> has been 
inactive for 30 minutes (no log file lines observed for that session).
.PP
Note that the log file line that has matched the first rule is also
matched against the second rule (since the first rule has the
.I continue
field set to TakeNext). 
Since the second rule always matches this line, it will become the first
line in the event store of
.BR ftp_<pid> .
The second rule has also its
.I continue
field set to TakeNext, since otherwise no log file lines would reach the 
third rule.
.SS "SINGLEWITHSCRIPT RULE"
The SingleWithScript rule supports the following fields.
Note that match variables may be used in
.IR context ,
.IR script ,
.IR desc ,
.IR action ,
and
.I action2
fields. 
.TP 
.I type
fixed to SingleWithScript (value is case insensitive).
.TP 
.IR continue " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive).
.TP 
.I ptype
pattern type (value is case insensitive).
.TP 
.I pattern
pattern.
.TP
.IR varmap " (optional)"
variable map.
.TP 
.IR context " (optional)"
context expression.
.TP 
.I script
command line of external program.
.TP
.IR shell " (optional)"
Yes or No (values are case insensitive, default is Yes).
.TP 
.I desc
operation description string.
.TP 
.I action
action list. 
.TP
.IR action2 " (optional)"
action list.
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B SingleWithScript
rule forks a process for executing an external program when an event has 
matched the rule. 
The command line of the external program is defined by the
.I script
field.
.PP
If the
.I shell
field is set to Yes (this is the default), the command line of the external
program will be parsed by shell if the command line contains shell 
metacharacters.
If the
.I shell
field is set to No, command line is not parsed by shell, but split into 
arguments by using whitespace as a separator, and passed to 
.BR execvp (3) 
for execution. Note that splitting into arguments is done when command
line is loaded from the configuration file and parsed, not at runtime
(e.g., if command line is
.IR "/usr/local/bin/mytool $1 $2" ,
the values of $1 and $2 variables are regarded as single arguments even if
the values contain whitespace).
.PP
The names of all currently existing contexts are written to the standard
input of the program.
After the program has been forked, the rule matching continues immediately, 
and the program status will be checked periodically until the program exits.
If the program returns 0 exit status, the action list defined by the
.I action
field is executed; otherwise the action list defined by the
.I action2
field is executed (if given).
.PP
Note that the SingleWithScript rule does not start event correlation 
operations, and the
.I desc
field is merely used for setting the %s action list variable.
.PP
.B Examples:
.PP
type=SingleWithScript
.br
ptype=RegExp
.br
pattern=interface ([\\d.]+) down
.br
script=/bin/ping -c 3 -q $1
.br
desc=Check if $1 responds to ping
.br
action=logonly Interface $1 reported down, but is pingable
.br
action2=pipe '%t: Interface $1 is down' /bin/mail root@localhost
.PP
When "interface <ipaddress> down" line appears in input, the rule checks
if <ipaddress> responds to ping. If <ipaddress> is pingable, the message
"Interface <ipaddress> reported down, but is pingable" is logged; otherwise
an e-mail warning containing a human-readable timestamp is sent to 
root@localhost.
.SS "SINGLEWITHSUPPRESS RULE"
The SingleWithSuppress rule supports the following fields.
Note that match variables may be used in
.IR context ,
.IR desc ,
and
.I action
fields.
.TP 
.I type
fixed to SingleWithSuppress (value is case insensitive).
.TP 
.IR continue " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive).
.TP 
.I ptype
pattern type (value is case insensitive).
.TP 
.I pattern
pattern.
.TP 
.IR varmap " (optional)"
variable map.
.TP 
.IR context " (optional)"
context expression.
.TP 
.I desc
operation description string.
.TP 
.I action
action list.
.TP 
.I window
event correlation window size (value is an integer constant).
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B SingleWithSuppress
rule runs event correlation operations for filtering repeated instances of
the same event during T seconds. The value of T is defined by the
.I window
field.
.PP
When an event has matched the rule, SEC evaluates the operation description 
string given with the
.I desc
field. If the operation for the given string and rule does not exist, 
SEC will create it with the lifetime of T seconds, and the operation 
immediately executes an action list. If the operation exists, it consumes 
the matching event without any action. 
.PP
.B Examples:
.PP
type=SingleWithSuppress
.br
ptype=RegExp
.br
pattern=(\\S+): [fF]ile system full
.br
desc=File system $1 full
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
window=900
.PP
This rule runs event correlation operations for processing "file system full"
syslog messages, e.g., 
.PP
Dec 16 14:26:09 test ufs: [ID 845546 kern.notice] NOTICE: alloc: /var: 
file system full
.PP
When the first message for a file system is observed, an operation is created 
which sends an e-mail warning about this file system to root@localhost. 
The operation will then run for 900 seconds and silently consume further 
messages for the *same* file system.
However, if a message for a different file system is observed, another 
operation will be started which sends a warning to root@localhost again
(since the
.I desc
field contains the $1 match variable which evaluates to the file system name).
.SS "PAIR RULE"
The Pair rule supports the following fields.
Note that match variables may be used in
.IR context ,
.IR desc ,
.IR action ,
.IR pattern2 ,
.IR context2 ,
.IR desc2 ,
and
.I action2
fields. 
.TP 
.I type
fixed to Pair (value is case insensitive).
.TP 
.IR continue " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive). Specifies the point-of-continue after a match by
.I pattern
and
.IR context .
.TP 
.I ptype
pattern type for
.I pattern
(value is case insensitive).
.TP 
.I pattern
pattern.
.TP 
.IR varmap " (optional)"
variable map for 
.IR pattern .
.TP 
.IR context " (optional)"
context expression, evaluated together with
.IR pattern .
.TP 
.I desc
operation description string.
.TP 
.I action
action list.
.TP
.IR continue2 " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive). Specifies the point-of-continue after a match by
.I pattern2
and
.IR context2 .
.TP
.I ptype2
pattern type for
.I pattern2
(value is case insensitive).
.TP 
.I pattern2
pattern.
.TP 
.IR varmap2 " (optional)"
variable map for
.IR pattern2 .
.TP 
.IR context2 " (optional)"
context expression, evaluated together with
.IR pattern2 .
.TP 
.I desc2
format string that sets the %s variable for
.IR action2 .
.TP 
.I action2
action list.
.TP 
.IR window " (optional)"
event correlation window size (value is an integer constant).
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B Pair
rule runs event correlation operations for processing event pairs 
during T seconds. The value of T is defined by the
.I window
field. Default value is 0 which means infinity.
.PP
When an event has matched the conditions defined by the
.I pattern
and
.I context
field, SEC evaluates the operation description string given with the
.I desc
field. 
If the operation for the given string and rule exists, it consumes 
the matching event without any action. If the operation does not exist, 
SEC will create it with the lifetime of T seconds, and the operation 
immediately executes an action list defined by the
.I action
field. SEC will also copy the match conditions given with the 
.I pattern2
and
.I context2
field into the operation, and substitute match variables with their values 
in copied conditions. 
.PP
If the event does not match conditions defined by the
.I pattern
and
.I context
field, SEC will check the match conditions of all operations started by 
the given rule. Each matching operation executes the action list given with the
.I action2
field and finishes. 
.PP
If match variables are set when the operation matches an event, they are
made available as $-prefixed match variables in
.IR context2 ,
.IR desc2 ,
and
.I action2
fields of the rule definition. For example, if 
.I pattern2
field is a regular expression, then $1 in the
.I desc2
field is set by
.IR pattern2 .
In order to access match variables set by 
.IR pattern ,
%-prefixed match variables have to be used in
.IR context2 ,
.IR desc2 ,
and
.I action2
fields. For example, if 
.I pattern
and
.I pattern2
are regular expressions, then %1 in the
.I desc2
field refers to the value set by the first capture group in
.I pattern
(i.e., it has the same value as $1 in the
.I desc
field).
.PP
.B Examples:
.PP
type=Pair
.br
ptype=RegExp
.br
pattern=kernel: nfs: server (\\S+) not responding, still trying
.br
desc=Server $1 is not responding
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
ptype2=SubStr
.br
pattern2=kernel: nfs: server $1 OK
.br
desc2=Server $1 is responding again
.br
action2=logonly
.br
window=3600
.PP
This rule runs event correlation operations for processing NFS "server not
responding" and "server OK" syslog messages, e.g.,
.PP
Dec 18 22:39:48 test kernel: nfs: server box1 not responding, still trying
.br
Dec 18 22:42:27 test kernel: nfs: server box1 OK
.PP
When the "server not responding" message for an NFS server is observed, 
an operation is created for this server which sends an e-mail warning about 
the server to root@localhost.
The operation will then run for 3600 seconds and silently consume further 
"server not responding" messages for the same server. If this operation
observes "server OK" message for the *same* server, it will log the message
"Server <servername> is responding again" and finish. 
.PP
For example, if SEC observes the following event at 22:39:48
.PP
Dec 18 22:39:48 test kernel: nfs: server box1 not responding, still trying
.PP
an event correlation operation is created for server box1 which issues
an e-mail warning about this server immediately. After that, the operation 
will run for 3600 seconds (until 23:39:48), waiting for an event which would 
contain the substring
"kernel: nfs: server box1 OK"
(because the
.I pattern2
field contains the $1 match variable which evaluates to the server name).
.PP
If any further error messages appear for server box1 during the 3600
second lifetime of the operation, e.g.,
.PP
Dec 18 22:40:28 test kernel: nfs: server box1 not responding, still trying
.br
Dec 18 22:41:09 test kernel: nfs: server box1 not responding, still trying
.PP
these messages will be silently consumed by the operation. 
If before its expiration the operation observes an event which contains 
the substring  "kernel: nfs: server box1 OK", e.g.,
.PP
Dec 18 22:42:27 test kernel: nfs: server box1 OK
.PP
the operation will log the message "Server box1 is responding again" 
and terminate immediately.
If no such message appears during the 3600 second lifetime of the operation,
the operation will expire without taking any action. Please note that if the
.I window
field would be either removed from the rule definition or set to 0, 
the operation would never silently expire, but would terminate only after 
observing an event which contains the substring  "kernel: nfs: server box1 OK".
.PP
If the above rule is modified in the following way
.PP
type=Pair
.br
ptype=RegExp
.br
pattern=^([[:alnum:]: ]+) \\S+ kernel: nfs: server (\\S+) not responding, still trying
.br
desc=Server $2 is not responding
.br
action=logonly
.br
ptype2=RegExp
.br
pattern2=^([[:alnum:]: ]+) \\S+ kernel: nfs: server $2 OK
.br
desc2=Server %2 was not accessible from %1 to $1
.br
action2=pipe '%s' /bin/mail root@localhost
.br
window=86400
.PP
this rule will run event correlation operations which report NFS server
downtime to root@localhost via e-mail, provided that downtime does not
exceed 24 hours (86400 seconds).
.PP
For example, if SEC observes the following event
.PP
Dec 18 23:01:17 test kernel: nfs: server box.test not responding, still trying
.PP
then the rule matches this event, sets $1 match variable to "Dec 18 23:01:17" 
and $2 to "box.test", and creates an event correlation operation for server 
box.test.
This operation will start its work by logging the message 
"Server box.test is not responding", and will then run for 86400 seconds, 
waiting for an event which would match the regular expression
.PP
^([[:alnum:]: ]+) \\S+ kernel: nfs: server box\\.test OK
.PP
Note that this expression was created from the regular expression template
in the
.I pattern2
field by substituting the match variable $2 with its value. However, since
the string "box.test" contains the dot (.) character which is a regular
expression metacharacter, the dot is masked with the backslash in the regular
expression.
.PP
Suppose SEC will then observe the event
.PP
Dec 18 23:09:54 test kernel: nfs: server box.test OK
.PP
This event matches the above regular expression which is used by the operation
running for server box.test. Also, the regular expression match sets the $1 
variable to "Dec 18 23:09:54" and unsets the $2 variable. In order to refer 
to their original values when the operation was created, %1 and %2 match 
variables have to be used in the 
.I desc2 
field (%1 equals to "Dec 18 23:01:17" and %2 equals to "box.test"). Therefore,
the operation will send the e-mail message "Server box.test was not accessible 
from Dec 18 23:01:17 to Dec 18 23:09:54" to root@localhost, and will terminate
immediately.
.SS "PAIRWITHWINDOW RULE"
The PairWithWindow rule supports the following fields.
Note that match variables may be used in
.IR context ,
.IR desc ,
.IR action ,
.IR pattern2 ,
.IR context2 ,
.IR desc2 ,
and
.I action2
fields. 
.TP 
.I type
fixed to PairWithWindow (value is case insensitive).
.TP 
.IR continue " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive). Specifies the point-of-continue after a match by
.I pattern
and
.IR context .
.TP 
.I ptype
pattern type for
.I pattern
(value is case insensitive).
.TP 
.I pattern
pattern.
.TP 
.IR varmap " (optional)"
variable map for 
.IR pattern .
.TP 
.IR context " (optional)"
context expression, evaluated together with
.IR pattern .
.TP 
.I desc
operation description string.
.TP 
.I action
action list.
.TP
.IR continue2 " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive). Specifies the point-of-continue after a match by
.I pattern2
and
.IR context2 .
.TP
.I ptype2
pattern type for
.I pattern2
(value is case insensitive).
.TP 
.I pattern2
pattern.
.TP 
.IR varmap2 " (optional)"
variable map for
.IR pattern2 .
.TP 
.IR context2 " (optional)"
context expression, evaluated together with
.IR pattern2 .
.TP 
.I desc2
format string that sets the %s variable for
.IR action2 .
.TP 
.I action2
action list.
.TP 
.I window
event correlation window size (value is an integer constant).
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B PairWithWindow
rule runs event correlation operations for processing event pairs
during T seconds. The value of T is defined by the
.I window
field.
.PP
When an event has matched the conditions defined by the
.I pattern
and
.I context
field, SEC evaluates the operation description string given with the
.I desc
field. 
If the operation for the given string and rule exists, it consumes 
the matching event without any action. If the operation does not exist, 
SEC will create it with the lifetime of T seconds. 
SEC will also copy the match conditions given with the 
.I pattern2
and
.I context2
field into the operation, and substitute match variables with their values 
in copied conditions. 
.PP
If the event does not match conditions defined by the
.I pattern
and
.I context
field, SEC will check the match conditions of all operations started by 
the given rule. Each matching operation executes the action list given with the
.I action2
field and finishes. 
If the operation has not observed a matching event by the end of its lifetime,
it executes the action list given with the 
.I action
field before finishing.
.PP
If match variables are set when the operation matches an event, they are
made available as $-prefixed match variables in
.IR context2 ,
.IR desc2 ,
and
.I action2
fields of the rule definition. For example, if 
.I pattern2
field is a regular expression, then $1 in the
.I desc2
field is set by 
.IR pattern2 .
In order to access match variables set by 
.IR pattern ,
%-prefixed match variables have to be used in
.IR context2 ,
.IR desc2 ,
and
.I action2
fields. For example, if 
.I pattern
and
.I pattern2
are regular expressions, then %1 in the
.I desc2
field refers to the value set by the first capture group in
.I pattern
(i.e., it has the same value as $1 in the
.I desc
field).
.PP
.B Examples:
.PP
type=PairWithWindow
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from ([\\d.]+) port \\d+ ssh2
.br
desc=User $1 has been unable to log in from $2 over SSH during 1 minute 
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
ptype2=RegExp
.br
pattern2=sshd\\[\\d+\\]: Accepted .+ for $1 from $2 port \\d+ ssh2
.br
desc2=SSH login successful for %1 from %2 after initial failure
.br
action2=logonly
.br
window=60
.PP
This rule runs event correlation operations for processing SSH login events,
e.g.,
.PP
Dec 27 19:00:24 test sshd[10526]: Failed password for risto from 10.1.2.7 port 52622 ssh2
.br
Dec 27 19:00:27 test sshd[10526]: Accepted password for risto from 10.1.2.7 port 52622 ssh2
.PP
When an SSH login failure is observed for a user name and a source IP address, 
an operation is created for this user name and IP address combination which 
will expect a successful login for the *same* user name and *same* IP address 
during 60 seconds.
If the user will not log in from the same IP address during 60 seconds, 
the operation will send an e-mail warning to root@localhost before finishing, 
otherwise it will log the message 
"SSH login successful for <username> from <ipaddress> after initial failure" 
and finish.
.PP
Suppose the following events are generated by an SSH daemon,
and each event timestamp reflects the time SEC observes the event:
.PP
Dec 30 13:02:01 test sshd[30517]: Failed password for risto from 10.1.2.7 port 42172 ssh2
.br
Dec 30 13:02:30 test sshd[30810]: Failed password for root from 192.168.1.104 port 46125 ssh2
.br
Dec 30 13:02:37 test sshd[30517]: Failed password for risto from 10.1.2.7 port 42172 ssh2
.br
Dec 30 13:02:59 test sshd[30810]: Failed password for root from 192.168.1.104 port 46125 ssh2
.br
Dec 30 13:03:04 test sshd[30810]: Accepted password for root from 192.168.1.104 port 46125 ssh2
.PP
When the first event is observed at 13:02:01, an operation is started for 
user risto and IP address 10.1.2.7 which will expect a successful login
for risto from 10.1.2.7. The operation will run for 60 seconds,
waiting for an event which would match the regular expression
.PP
sshd\\[\\d+\\]: Accepted .+ for risto from 10\\.1\\.2\\.7 port \\d+ ssh2
.PP
Note that this expression was created from the regular expression template
in the
.I pattern2
field by substituting match variables $1 and $2 with their values. However, 
since the value of $2 contains the dot (.) characters which are regular
expression metacharacters, each dot is masked with the backslash in the regular
expression.
.PP
When the second event is observed at 13:02:30, another operation is started
for user root and IP address 192.168.1.104 which will expect root
to log in successfully from 192.168.1.104. This operation will run for
60 seconds, waiting for an event matching the regular expression
.PP
sshd\\[\\d+\\]: Accepted .+ for root from 192\\.168\\.1\\.104 port \\d+ ssh2
.PP
The third event at 13:02:37 represents a second login failure for user
risto and IP address 10.1.2.7, and is silently consumed by the first 
operation. Likewise, the fourth event at 13:02:59 is silently consumed
by the second operation.
The first operation will run until 13:03:01 and then expire without seeing 
a successful login for risto from 10.1.2.7. Before terminating, the operation 
will send an e-mail warning to root@localhost that user risto has not
managed to log in from 10.1.2.7 during one minute.
At 13:03:04, the second operation will observe an event which matches
its regular expression
.PP
sshd\\[\\d+\\]: Accepted .+ for root from 192\\.168\\.1\\.104 port \\d+ ssh2
.PP
After seeing this event, the operation will log the message
"SSH login successful for root from 192.168.1.104 after initial failure"
and terminate immediately.
Please note that the match by the regular expression 
.PP
sshd\\[\\d+\\]: Accepted .+ for root from 192\\.168\\.1\\.104 port \\d+ ssh2
.PP
sets the $1 match variable to 1 and unsets $2. Therefore, the %1 and %2
match variables have to be used in the 
.I desc2
field, in order to refer to the original values of $1 (root) and $2
(192.168.1.104) when the operation was created.
.SS "SINGLEWITHTHRESHOLD RULE"
The SingleWithThreshold rule supports the following fields.
Note that match variables may be used in
.IR context ,
.IR desc ,
.IR action ,
and
.I action2
fields.
.TP 
.I type
fixed to SingleWithThreshold (value is case insensitive).
.TP 
.IR continue " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive).
.TP 
.I ptype
pattern type (value is case insensitive).
.TP 
.I pattern
pattern.
.TP 
.IR varmap " (optional)"
variable map.
.TP 
.IR context " (optional)"
context expression.
.TP 
.I desc
operation description string.
.TP 
.I action
action list.
.TP 
.IR action2 " (optional)"
action list.
.TP 
.I window
event correlation window size (value is an integer constant).
.TP 
.I thresh
counting threshold (value is an integer constant).
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B SingleWithThreshold
rule runs event correlation operations for counting repeated instances of the
same event during T seconds, and taking an action if N events are observed. 
The values of T and N are defined by the
.I window
and
.I thresh
field, respectively.
.PP
When an event has matched the rule, SEC evaluates the operation description 
string given with the 
.I desc 
field. If the operation for the given string and rule does not exist, 
SEC will create it with the lifetime of T seconds. The operation will 
memorize the occurrence time of the event (current time as returned by the
.BR time (2)
system call), and compare the number of memorized occurrence times with 
the threshold N. If the operation has observed N events, it executes the
action list defined by the
.I action
field, and consumes all further matching events without any action. If the
rule has an optional action list defined with the
.I action2
field, the operation will execute it before finishing, provided that the
action list given with
.I action
has been previously executed by the operation. Note that  a sliding 
window is employed for event counting -- if the operation has observed 
less than N events by the end of its lifetime, it drops occurrence times which
are older than T seconds, and extends its lifetime for T seconds from the
earliest remaining occurrence time. If there are no remaining occurrence
times, the operation finishes without executing an action list. 
.PP
.B Examples:
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from [\\d.]+ port \\d+ ssh2
.br
desc=Three SSH login failures within 1m for user $1
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
window=60
.br
thresh=3
.PP
This rule runs event correlation operations for counting the number of SSH
login failure events. Each operation counts events for one user name, and
if the operation has observed three login failures within 60 seconds,
it sends an e-mail warning to root@localhost. 
.PP
Suppose the following events are generated by an SSH daemon,
and each event timestamp reflects the time SEC observes the event:
.PP
Dec 28 01:42:21 test sshd[28132]: Failed password for risto from 10.1.2.7 port 42172 ssh2
.br
Dec 28 01:43:10 test sshd[28132]: Failed password for risto from 10.1.2.7 port 42172 ssh2
.br
Dec 28 01:43:29 test sshd[28132]: Failed password for risto from 10.1.2.7 port 42172 ssh2
.br
Dec 28 01:44:00 test sshd[28149]: Failed password for risto2 from 10.1.2.7 port 42176 ssh2
.br
Dec 28 01:44:03 test sshd[28211]: Failed password for risto from 10.1.2.7 port 42192 ssh2
.br
Dec 28 01:44:07 test sshd[28211]: Failed password for risto from 10.1.2.7 port 42192 ssh2
.PP
When the first event is observed at 01:42:21, a counting operation is started 
for user risto, with its event correlation window ending at 01:43:21.
Since by 01:43:21 two SSH login failures for user risto have occurred, 
the threshold condition remains unsatisfied for the operation. 
Therefore, the beginning of its event correlation window will be moved 
to 01:43:10
(the occurrence time of the second event), leaving the first event outside 
the window.
At 01:44:00, another counting operation is started for user risto2.
The threshold condition for the first operation will become satisfied 
at 01:44:03 (since the operation has seen three login failure events for
user risto within 60 seconds), 
and thus an e-mail warning will be issued. Finally, the event occurring 
at 01:44:07 will be consumed silently by the first operation (the operation 
will run until 01:44:10).
Since there will be no further login failure events for user risto2,
the second operation will exist until 01:45:00 without taking any action.
.SS "SINGLEWITH2THRESHOLDS RULE"
The SingleWith2Thresholds rule supports the following fields.
Note that match variables may be used in
.IR context ,
.IR desc ,
.IR action ,
.IR desc2 ,
and
.I action2
fields.
.TP 
.I type
fixed to SingleWith2Thresholds (value is case insensitive).
.TP 
.IR continue " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive).
.TP 
.I ptype
pattern type (value is case insensitive).
.TP 
.I pattern
pattern.
.TP 
.IR varmap " (optional)"
variable map.
.TP 
.IR context " (optional)"
context expression.
.TP 
.I desc
operation description string.
.TP 
.I action
action list.
.TP 
.I window
event correlation window size (value is an integer constant).
.TP 
.I thresh
counting threshold.
.TP 
.I desc2
format string that sets the %s variable for
.IR action2 .
.TP 
.I action2
action list. 
.TP 
.I window2
event correlation window size (value is an integer constant).
.TP 
.I thresh2
counting threshold.
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B SingleWith2Thresholds
rule runs event correlation operations which take action if N1 events have 
been observed in the window of T1 seconds, and then at most N2 events will
be observed in the window of T2 seconds. 
The values of T1, N1, T2, and N2 are defined by the
.IR window ,
.IR thresh ,
.IR window2 ,
and
.I thresh2
field, respectively.
.PP
When an event has matched the rule, SEC evaluates the operation description 
string given with the 
.I desc 
field. If the operation for the given string and rule does not exist, 
SEC will create it with the lifetime of T1 seconds. The operation will 
memorize the occurrence time of the event (current time as returned by the
.BR time (2)
system call), and compare the number of memorized occurrence times with 
the threshold N1. If the operation has observed N1 events, it executes the
action list defined by the
.I action
field, and starts another counting round for T2 seconds.
If no more than N2 events have been observed by the end of the window, 
the operation executes the action list defined by the
.I action2
field and finishes. Note that both windows are sliding -- the first window
slides like the window of the SingleWithThreshold operation, while the 
beginning of the second window is moved to the second earliest memorized
event occurrence time when the threshold N2 is violated.
.PP
.B Examples:
.PP
type=SingleWith2Thresholds
.br
ptype=RegExp 
.br
pattern=(\\S+): %SYS-3-CPUHOG
.br
desc=Router $1 CPU overload
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
window=300
.br
thresh=2
.br
desc2=Router $1 CPU load has been normal for 1h
.br
action2=logonly
.br
window2=3600
.br
thresh2=0
.PP
When a SYS-3-CPUHOG syslog message is received from a router, the rule starts 
a counting operation for this router which sends an e-mail warning to
root@localhost if another such message is received from the same router
within 300 seconds. After sending the warning, the operation will continue to
run until no SYS-3-CPUHOG syslog messages have been received from the router 
for 3600 seconds. When this condition becomes satisfied, the operation will log 
the message "Router <routername> CPU load has been normal for 1h" and finish.
.PP
Suppose the following events are generated by a router,
and each event timestamp reflects the time SEC observes the event:
.PP
Dec 30 12:23:25 router1.mydomain Router1: %SYS-3-CPUHOG: cpu is hogged
.br
Dec 30 12:25:38 router1.mydomain Router1: %SYS-3-CPUHOG: cpu is hogged
.br
Dec 30 12:28:53 router1.mydomain Router1: %SYS-3-CPUHOG: cpu is hogged
.PP
When the first event is observed at 12:23:25, a counting operation is started
for router Router1. The appearance of the second event at 12:25:38
fulfills the threshold condition given with the 
.I thresh
and
.I window
fields (two events have been observed within 300 seconds). Therefore, 
the operation will send an e-mail warning about the CPU overload of Router1
to root@localhost. 
.PP
After that, the operation will start another counting round, expecting to see 
no SYS-3-CPUHOG events (since 
.IR thresh2=0 )
for Router1 during the following 3600 seconds (the beginning of 
the operation's event correlation window will be moved to 12:25:38 for 
the second counting round).
Since the appearance of the third event at 12:28:53 violates the threshold 
condition given with the
.I thresh2
and
.I window2
fields, the beginning of the event correlation window will be moved 
to 12:28:53.
Since there will be no further SYS-3-CPUHOG messages for Router1,
the operation will run until 13:28:53 and then expire, logging the message
"Router Router1 CPU load has been normal for 1h" before finishing.
.SS "EVENTGROUP RULE"
The EventGroup rule supports the following fields.
Note that match variables may be used in
.IR context* ,
.IR count* ,
.IR egtoken* ,
.IR desc ,
.IR action ,
.IR init ,
.IR end ,
and
.I slide
fields.
.TP 
.I type 
.IR "" "EventGroup[" N "]"
(value is case insensitive, N defaults to 1).
.TP 
.IR continue " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive). Specifies the point-of-continue after a match by
.I pattern
and
.IR context .
.TP 
.I ptype
pattern type for
.I pattern
(value is case insensitive).
.TP 
.I pattern
pattern.
.TP 
.IR varmap " (optional)"
variable map for
.IR pattern .
.TP 
.IR context " (optional)"
context expression, evaluated together with
.IR pattern .
.TP 
.IR count " (optional)"
action list for execution after a match by
.I pattern
and
.IR context .
.TP
.IR thresh " (optional)"
counting threshold for events matched by
.I pattern
and
.I context 
(value is an integer constant, default is 1).
.TP
.IR egtoken " (optional)"
token for building the event group string that is matched with
.I egpattern 
(default value is 1).
.TP
.B ...
.TP 
.IR continueN " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive). Specifies the point-of-continue after a match by
.I patternN
and
.IR contextN .
.TP 
.I ptypeN
pattern type for
.I patternN
(value is case insensitive).
.TP 
.I patternN
pattern.
.TP 
.IR varmapN " (optional)"
variable map for
.IR patternN .
.TP 
.IR contextN " (optional)"
context expression, evaluated together with
.IR patternN .
.TP 
.IR countN " (optional)"
action list for execution after a match by
.I patternN
and
.IR contextN .
.TP
.IR threshN " (optional)"
counting threshold for events matched by
.I patternN
and
.I contextN
(value is an integer constant, default is 1).
.TP
.IR egtokenN " (optional)"
token for building the event group string that is matched with
.I egpattern
(default value is N).
.TP 
.I desc
operation description string.
.TP 
.I action
action list.
.TP 
.IR init " (optional)"
action list.
.TP 
.IR end " (optional)"
action list.
.TP 
.IR slide " (optional)"
action list.
.TP
.IR multact " (optional)"
Yes or No (values are case insensitive, default is No).
.TP
.IR egptype " (optional)"
SubStr, NSubStr, RegExp, NRegExp, PerlFunc or NPerlFunc
(values are case insensitive).
Specifies the pattern type for
.IR egpattern .
.TP
.IR egpattern " (optional)"
event group pattern.
.TP 
.I window
event correlation window size (value is an integer constant).
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B EventGroup
rule runs event correlation operations for counting repeated instances of
N different events e1,...,eN during T seconds, and taking an action if 
threshold conditions c1,...,cN for *all* events are satisfied (i.e., for 
each event eK there are at least cK event instances in the window).
Note that the event correlation window of the EventGroup operation 
is sliding like the window of the SingleWithThreshold operation.
.PP
Event e1 is described with the 
.I pattern
and
.I context
field, event e2 is described with the
.I pattern2
and
.I context2
field, etc.
The values for N and T are defined by the
.I type
and 
.I window
field, respectively. The value for c1 is given with the 
.I thresh
field, the value for c2 is given with the
.I thresh2
field, etc. 
Values for N and c1,...,cN default to 1. 
.PP
In order to match an event with the rule, 
.I pattern
and
.I context
fields are evaluated first. If they don't match the event, then
.I pattern2
and
.I context2
are evaluated, etc. If all N conditions are tried without a success,
the event doesn't match the rule.
.PP
When an event has matched the rule, SEC evaluates the operation description 
string given with the 
.I desc 
field. If the operation for the given string and rule does not exist, 
SEC will create it with the lifetime of T seconds. The operation will 
memorize the occurrence time of the event (current time as returned by the
.BR time (2)
system call), and compare the number of memorized occurrence times for each
eK with the threshold cK (i.e., the number of observed instances of eK is 
compared with the threshold cK).
If all threshold conditions are satisfied, the operation executes the
action list defined by the
.I action
field, and consumes all further matching events without re-executing
the action list if the
.I multact
field is set to No (this is the default). 
However, if
.I multact
is set to Yes, the operation will re-evaluate the threshold conditions on 
every further matching event, re-executing the action list given with the
.I action
field if all conditions are satisfied, and sliding the event correlation 
window forward when the window is about to expire (if no events remain in
the window, the operation will finish).
.PP
For example, consider the following rule:
.PP
type=EventGroup2
.br
ptype=SubStr
.br
pattern=EVENT_A
.br
thresh=2
.br
ptype2=SubStr
.br
pattern2=EVENT_B
.br
thresh2=2
.br
desc=Sequence of two or more As and Bs observed within 60 seconds
.br
action=write - %s
.br
window=60
.PP
Also, suppose the following events occur, and each event timestamp reflects 
the time SEC observes the event: 
.PP
Mar 10 12:03:01 EVENT_A
.br
Mar 10 12:03:04 EVENT_B
.br
Mar 10 12:03:10 EVENT_A
.br
Mar 10 12:03:11 EVENT_A
.br
Mar 10 12:03:27 EVENT_B
.br
Mar 10 12:03:46 EVENT_A
.br
Mar 10 12:03:59 EVENT_A
.PP
When these events are observed by the above EventGroup2 rule, the rule
starts an event correlation operation at 12:03:01. Note that although
the first threshold condition 
.I thresh=2 
is satisfied when the third
event appears at 12:03:10, the second threshold condition 
.I thresh2=2
is not met, and therefore the operation will not execute the action list
given with the 
.I action
field.
When the fifth event appears at 12:03:27, all threshold conditions are
finally satisfied, and the operation will write the string
"Sequence of two or more As and Bs observed within 60 seconds"
to standard output with the
.I write
action. Finally, the events occurring at 12:03:46 and 12:03:59
will be consumed silently by the operation (the operation will run until
12:04:01).
.PP
If
.I multact=yes
statement is added to the above EventGroup2 rule, the operation would
execute the 
.I write
action not only at 12:03:27, but also at 12:03:46 and 12:03:59, since
all threshold conditions are still satisfied when the last two events appear
(i.e., the last two events are no longer silently consumed). Also, with
.I multact=yes
the operation will employ sliding window based event processing even after 
the 
.I write
action has been executed at 12:03:27 (therefore, the operation will run 
until 12:04:59).
.PP
If the rule definition has an optional event group pattern and its type
defined with the
.I egpattern
and
.I egptype
fields, the event group pattern is used for matching the event group string.
The event group string consists of tokens Xi that are separated 
by a single space character:
"X1 X2 ... XM". 
M is the number of events a given event correlation operation has observed 
within its event correlation window. 
.PP
If the i-th event that the event
correlation operation has observed is an instance of event eK, then Xi is set
as follows. If the rule definition has a token defined with the
.I egtokenK
field for event eK, Xi is set to that token (the token definition may contain 
match variables that are substituted with values from matching the current
instance of eK). 
If the rule does not have the
.I egtokenK
field, then Xi = K (note that K is a positive integer).
.PP
Event group string is built and matched with event group pattern after all
threshold conditions (given with
.I thresh*
fields) have been found satisfied. 
In other words, the event group pattern defines an additional condition 
to numeric threshold conditions. 
.PP
Note that the event group pattern
and its type are similar to regular patterns and pattern types that are 
given with
.I pattern*
and
.I ptype*
fields, except the event group pattern is not setting any match variables. 
If the
.I egptype
field is set to RegExp or NRegExp, the
.I egpattern 
field defines a regular expression, while in the case of SubStr and NSubStr
.I egpattern
provides a string pattern.
.PP
If the
.I egptype
field is set to PerlFunc or NPerlFunc, the Perl function given with the
.I egpattern
field is called in the Perl scalar context, with the function having three
parameters: the event group string, the reference to the list of tokens 
from the event group string, and the reference to the list of event
occurrence times that correspond to tokens. 
Each event occurrence time is provided in seconds since Epoch, 
with the first element in the list being the occurrence time
of the event represented by the first token in the event group string,
the second element in the list being the occurrence time of the event
represented by the second token in the event group string, etc. 
.PP
With 
.IR egptype=PerlFunc ,
event group pattern matches if the return value of the function evaluates 
true in the Perl boolean context, while in the case of false the pattern 
does not match the event group string.
With 
.IR egptype=NPerlFunc ,
the pattern matching works in the opposite way.
.PP
For example, consider the following rule:
.PP
type=EventGroup2
.br
ptype=SubStr
.br
pattern=EVENT_A
.br
thresh=2
.br
ptype2=SubStr
.br
pattern2=EVENT_B
.br
thresh2=2
.br
desc=Sequence of two or more As and Bs with 'A B' at the end
.br
action=write - %s
.br
egptype=RegExp
.br
egpattern=1 2$
.br
window=60
.PP
Also, suppose the following events occur, and each event timestamp reflects 
the time SEC observes the event: 
.PP
Mar 10 12:05:31 EVENT_B
.br
Mar 10 12:05:32 EVENT_B
.br
Mar 10 12:05:38 EVENT_A
.br
Mar 10 12:05:39 EVENT_A
.br
Mar 10 12:05:42 EVENT_B
.PP
When these events are observed by the above EventGroup2 rule, the rule
starts an event correlation operation at 12:05:31. When the fourth event
appears at 12:05:39, all threshold conditions
.IR "" ( thresh=2
and
.IR thresh2=2 )
become satisfied, and therefore the following event group string is built 
from the first four events:
.PP
2 2 1 1
.PP
However, since this string does not match the regular expression
.PP
1 2$
.PP
that has been given with the
.I egpattern
field, the operation will not execute the action list given with the 
.I action
field. When the fifth event appears at 12:05:42, all threshold conditions 
are again satisfied, and all observed events produce the following 
event group string:
.PP
2 2 1 1 2
.PP
Since this event group string matches the regular expression given with the
.I egpattern
field, the operation will write the string
"Sequence of two or more As and Bs with 'A B' at the end"
to standard output with the
.I write
action.
.PP
If the rule definition has an optional action list defined with the
.I countK
field for event eK, the operation executes it every time an instance of eK 
is observed (even if
.I multact
is set to No and the operation has already executed the action list given
with
.IR action ).
If the action list contains match variables, they are substituted before
*each* execution with values from matching the current instance of eK.
.PP
If the rule definition has an optional action list defined with the
.I init
field, the operation executes it immediately after the operation has been
created. 
.PP
If the rule definition has an optional action list defined with the
.I end
field, the operation executes it immediately before the operation finishes.
Note that this action list is *not* executed when the operation is
terminated with the
.I reset
action.
.PP
If the rule definition has an optional action list defined with the
.I slide
field, the operation executes it immediately after the event correlation 
window has slidden forward.
However, note that moving the window with the
.I setwpos
action will *not* trigger the execution.
.PP
Also note that when the event correlation window slides forward, 
the event group pattern (given with the
.I egpattern
field) and numeric threshold conditions (given with
.I thresh*
fields) will *not* be evaluated for checking if the action list given with the
.I action
field should be executed.
.PP
.B Examples:
.PP
The following example rule cross-correlates iptables events,
Apache web server access log messages with 4xx response codes,
and SSH login failure events:
.PP
type=EventGroup3
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (?:invalid user )?\\S+ from ([\\d.]+) port \\d+ ssh2
.br
thresh=2
.br
ptype2=RegExp
.br
pattern2=^([\\d.]+) \\S+ \\S+ \\[.+?\\] ".+? HTTP\\/[\\d.]+" 4\\d+
.br
thresh2=3
.br
ptype3=RegExp
.br
pattern3=kernel: iptables:.* SRC=([\\d.]+)
.br
thresh3=5
.br
desc=Repeated probing from host $1
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
window=120
.PP
The rule starts an event correlation operation for an IP address if SSH login
failure event, iptables event, or Apache 4xx event is observed 
for that IP address. The operation sends an e-mail warning to root@localhost
if within 120 seconds three threshold conditions are satisfied for the IP
address it tracks -- 
(1) at least two SSH login failure events have occurred for this client IP,
(2) at least three Apache 4xx events have occurred for this client IP, 
(3) at least five iptables events have been observed for this source IP. 
.PP
Suppose the following events occur, and each event timestamp reflects 
the time SEC observes the event: 
.PP
192.168.1.104 - - [05/Jan/2014:01:11:22 +0200] "GET /test.html HTTP/1.1" 404 286 "-" "Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:26.0) Gecko/20100101 Firefox/26.0"
.br
Jan  5 01:12:52 localhost kernel: iptables: IN=eth0 OUT= MAC=08:00:27:8e:a1:3a:00:1d:e0:7e:89:b1:08:00 SRC=192.168.1.104 DST=192.168.1.107 LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=48422 DF PROTO=TCP SPT=46351 DPT=21 WINDOW=29200 RES=0x00 SYN URGP=0 
.br
Jan  5 01:12:53 localhost kernel: iptables: IN=eth0 OUT= MAC=08:00:27:8e:a1:3a:00:1d:e0:7e:89:b1:08:00 SRC=192.168.1.104 DST=192.168.1.107 LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=48423 DF PROTO=TCP SPT=46351 DPT=21 WINDOW=29200 RES=0x00 SYN URGP=0 
.br
Jan  5 01:13:01 localhost kernel: iptables: IN=eth0 OUT= MAC=08:00:27:8e:a1:3a:00:1d:e0:7e:89:b1:08:00 SRC=192.168.1.104 DST=192.168.1.107 LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=20048 DF PROTO=TCP SPT=44963 DPT=23 WINDOW=29200 RES=0x00 SYN URGP=0 
.br
Jan  5 01:13:02 localhost kernel: iptables: IN=eth0 OUT= MAC=08:00:27:8e:a1:3a:00:1d:e0:7e:89:b1:08:00 SRC=192.168.1.104 DST=192.168.1.107 LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=20049 DF PROTO=TCP SPT=44963 DPT=23 WINDOW=29200 RES=0x00 SYN URGP=0 
.br
Jan  5 01:13:08 localhost kernel: iptables: IN=eth0 OUT= MAC=08:00:27:8e:a1:3a:00:1d:e0:7e:89:b1:08:00 SRC=192.168.1.104 DST=192.168.1.107 LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=36362 DF PROTO=TCP SPT=56918 DPT=25 WINDOW=29200 RES=0x00 SYN URGP=0 
.br
Jan  5 01:13:09 localhost kernel: iptables: IN=eth0 OUT= MAC=08:00:27:8e:a1:3a:00:1d:e0:7e:89:b1:08:00 SRC=192.168.1.104 DST=192.168.1.107 LEN=60 TOS=0x10 PREC=0x00 TTL=64 ID=36363 DF PROTO=TCP SPT=56918 DPT=25 WINDOW=29200 RES=0x00 SYN URGP=0
.br
192.168.1.104 - - [05/Jan/2014:01:13:51 +0200] "GET /test.html HTTP/1.1" 404 286 "-" "Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:26.0) Gecko/20100101 Firefox/26.0"
.br
192.168.1.104 - - [05/Jan/2014:01:13:54 +0200] "GET /test.html HTTP/1.1" 404 286 "-" "Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:26.0) Gecko/20100101 Firefox/26.0"
.br
192.168.1.104 - - [05/Jan/2014:01:14:00 +0200] "GET /login.html HTTP/1.1" 404 287 "-" "Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:26.0) Gecko/20100101 Firefox/26.0"
.br
192.168.1.104 - - [05/Jan/2014:01:14:03 +0200] "GET /login.html HTTP/1.1" 404 287 "-" "Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:26.0) Gecko/20100101 Firefox/26.0"
.br
192.168.1.104 - - [05/Jan/2014:01:14:03 +0200] "GET /login.html HTTP/1.1" 404 287 "-" "Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:26.0) Gecko/20100101 Firefox/26.0"
.br
Jan  5 01:14:11 localhost sshd[1810]: Failed password for root from 192.168.1.104 port 46125 ssh2
.br
Jan  5 01:14:12 localhost sshd[1810]: Failed password for root from 192.168.1.104 port 46125 ssh2
.br
Jan  5 01:14:18 localhost sshd[1822]: Failed password for root from 192.168.1.104 port 46126 ssh2
.br
Jan  5 01:14:19 localhost sshd[1822]: Failed password for root from 192.168.1.104 port 46126 ssh2
.br
192.168.1.104 - - [05/Jan/2014:01:14:34 +0200] "GET /test.html HTTP/1.1" 404 286 "-" "Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:26.0) Gecko/20100101 Firefox/26.0"
.PP
The Apache 4xx event at 01:11:22 starts an event correlation operation 
for 192.168.1.104 which has the event correlation window of 120 seconds,  
thus ending at 01:13:22.
Between 01:12:52 and 01:13:09, six iptables events appear for 192.168.1.104,
and the appearance of the fifth event at 01:13:08 fulfills the third threshold
condition (within 120 seconds, at least five iptables events have been
observed). 
.PP
Since by 01:13:22 (the end of the event correlation window) no additional
events have occurred, the first and second threshold condition
remain unsatisfied. 
Therefore, the beginning of the event correlation window will be moved 
to 01:12:52
(the occurrence time of the earliest event which is at most 120 seconds old).
As a result, the end of the window will move from 01:13:22 to 01:14:52.
The only event which is left outside the window is the Apache 4xx event
at 01:11:22, and thus the threshold condition for iptables events 
remains satisfied.
.PP
Between 01:13:51 and 01:14:03, five Apache 4xx events occur, and the appearance
of the third event at 01:14:00 fulfills the second threshold condition
(within 120 seconds, at least three Apache 4xx events have been observed).
These events are followed by four SSH login failure events which occur
between 01:14:11 and 01:14:19. The appearance of the second event at 01:14:12 
fulfills the first threshold condition
(within 120 seconds, at least two SSH login failure events have been observed). 
Since at this particular moment (01:14:12) the other two conditions are also 
fulfilled, the operation sends an e-mail warning about 192.168.1.104 
to root@localhost. 
After that, the operation silently consumes all further matching events 
for 192.168.1.104 until 01:14:52, and then terminates.
.PP
Please note that if the above rule definition would contain
.I multact=yes
statement, the operation would continue sending e-mails at each matching 
event after 01:14:12, provided that all threshold conditions are satisfied.
Therefore, the operation would send three additional e-mails at 01:14:18,
01:14:19, and 01:14:34. 
Also, the operation would not terminate after its window ends at 01:14:52,
but would rather slide the window forward and expect new events.
At the occurrence of any iptables, SSH login failure or Apache 4xx event
for 192.168.1.104, the operation would produce a warning e-mail
if all threshold conditions are fulfilled.
.PP
The following example rule cross-correlates iptables events and SSH login 
events:
.PP
type=EventGroup3
.br
ptype=regexp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from ([\\d.]+) port \\d+ ssh2
.br
varmap= user=1; ip=2
.br
count=alias OPER_$+{ip} LOGIN_FAILED_$+{user}_$+{ip}
.br
ptype2=regexp
.br
pattern2=sshd\\[\\d+\\]: Accepted .+ for (\\S+) from ([\\d.]+) port \\d+ ssh2
.br
varmap2= user=1; ip=2
.br
context2=LOGIN_FAILED_$+{user}_$+{ip}
.br
ptype3=regexp
.br
pattern3=kernel: iptables:.* SRC=([\\d.]+)
.br
varmap3= ip=1
.br
desc=Client $+{ip} accessed a firewalled port and had difficulties with logging in
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
init=create OPER_$+{ip}
.br
slide=delete OPER_$+{ip}; reset 0
.br
end=delete OPER_$+{ip}
.br
window=120
.PP
The rule starts an event correlation operation for an IP address if SSH login
failure or iptables event was observed for that IP address. The operation 
exists for 120 seconds (since when the event correlation window slides 
forward, the operation terminates itself with the
.I reset 
action as specified with the
.I slide
field).
The operation sends an e-mail warning to root@localhost if within 120 seconds 
three threshold conditions are satisfied for the IP address it tracks -- 
(1) at least one iptables event has been observed for this source IP, 
(2) at least one SSH login failure has been observed for this client IP, 
(3) at least one successful SSH login has been observed for this client IP 
and for some user, provided that the operation has previously observed
an SSH login failure for the same user and same client IP.
.PP
Suppose the following events occur, and each event timestamp reflects 
the time SEC observes the event: 
.PP
Dec 27 19:00:06 test kernel: iptables: IN=eth0 OUT= MAC=00:13:72:8a:83:d2:00:1b:25:07:e2:1b:08:00 SRC=10.1.2.7 DST=10.2.5.5 LEN=60 TOS=0x00 PREC=0x00 TTL=62 ID=1881 DF PROTO=TCP SPT=34342 DPT=23 WINDOW=5840 RES=0x00 SYN URGP=0
.br
Dec 27 19:00:14 test sshd[10520]: Accepted password for root from 10.1.2.7 port 52609 ssh2
.br
Dec 27 19:00:24 test sshd[10526]: Failed password for risto from 10.1.2.7 port 52622 ssh2
.br
Dec 27 19:00:27 test sshd[10526]: Accepted password for risto from 10.1.2.7 port 52622 ssh2
.PP
The iptables event at 19:00:06 starts an event correlation operation 
for 10.1.2.7 which has the event correlation window of 120 seconds.
Immediately after the operation has been started, it creates the context 
OPER_10.1.2.7.
The second event at 19:00:14 does not match the rule, since
the context LOGIN_FAILED_root_10.1.2.7 does not exist.
The third event at 19:00:24 matches the rule, and the operation which
is running for 10.1.2.7 sets up the alias name LOGIN_FAILED_risto_10.1.2.7 
for the context OPER_10.1.2.7.
Finally, the fourth event at 19:00:27 matches the rule, since the context
LOGIN_FAILED_risto_10.1.2.7 exists, and the event is therefore processed
by the operation (the presence of the context indicates that the operation
has previously observed a login failure for user risto from 10.1.2.7).
At this particular moment (19:00:27), all three threshold conditions for
the operation are fulfilled, and therefore it sends an e-mail warning 
about 10.1.2.7 to root@localhost. After that, the operation silently consumes 
all further matching events for 10.1.2.7 until 19:02:06, and then terminates. 
Immediately before termination, the operation deletes the context OPER_10.1.2.7
which also drops its alias name LOGIN_FAILED_risto_10.1.2.7.
.PP
The following example rule correlates SSH login failure events:
.PP
type=EventGroup
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from ([\\d.]+) port \\d+ ssh2
.br
desc=SSH login failures from three different hosts within 1m for user $1
.br
egtoken=$2
.br
egptype=PerlFunc
.br
egpattern=sub { my(%hosts) = map { $_ => 1 } @{$_[1]}; \\
                return scalar(keys %hosts) >= 3; }
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
window=60
.br
thresh=3
.PP
The rule runs event correlation operations for counting the number of SSH
login failure events. Each operation counts events for one user name, and
if the operation has observed login failures from three different hosts 
within 60 seconds, it sends an e-mail warning to root@localhost. 
For verifying that hosts are different, the
.I egtoken
field configures the use of host IP addresses as tokens for building 
the event group string. Also, the Perl function provided with the
.I egpattern 
field checks if the list of tokens contains at least three unique IP addresses.
Note that the list of tokens is referenced by the second input parameter 
($_[1]) of the function, while the first input parameter ($_[0]) holds 
the event group string (the above Perl function only processes the list of 
tokens).
.PP
Suppose the following events are generated by an SSH daemon,
and each event timestamp reflects the time SEC observes the event:
.PP
Apr  4 23:04:00 test sshd[21137]: Failed password for risto from 10.1.1.7 port 32182 ssh2
.br
Apr  4 23:04:03 test sshd[21145]: Failed password for risto from 10.1.1.9 port 42176 ssh2
.br
Apr  4 23:04:04 test sshd[21212]: Failed password for risto from 10.1.1.7 port 34191 ssh2
.br
Apr  4 23:04:07 test sshd[21226]: Failed password for risto from 10.1.1.2 port 18999 ssh2
.PP
When the first event is observed at 23:04:00, a counting operation is started 
for user risto. Since at 23:04:04 the operation observes the third event,
the threshold condition given with the
.I thresh
field becomes satisfied, and thus the event group pattern given with the 
.I egpattern
field is evaluated. However, the list of tokens (10.1.1.7, 10.1.1.9, 10.1.1.7)
contains only two unique elements, and therefore the event group pattern does 
not match.
When the fourth event occurs at 23:04:07, event group pattern is evaluated
again, and since the list of tokens (10.1.1.7, 10.1.1.9, 10.1.1.7, 10.1.1.2) 
contains three unique elements now, the event group pattern matches and
the operation will send an e-mail warning to root@localhost.
.SS "SUPPRESS RULE"
The Suppress rule supports the following fields.
Note that match variables may be used in the
.I context
field. 
.TP 
.I type
fixed to Suppress (value is case insensitive).
.TP 
.I ptype
pattern type (value is case insensitive).
.TP 
.I pattern
pattern.
.TP 
.IR varmap " (optional)"
variable map.
.TP 
.IR context " (optional)"
context expression.
.TP
.IR desc " (optional)"
string for describing the rule.
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B Suppress
rule takes no action when an event has matched the rule, and keeps
matching events from being processed by later rules in the configuration file. 
.PP
Note that the Suppress rule does not start event correlation operations,
and the optional
.I desc
field is merely used for describing the rule.
Also, in order to end event processing, so that no further rules from
any of the configuration files would be tried, use the Jump rule.
.PP
.B Examples:
.PP
type=Suppress
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for \\S+ from ([\\d.]+) port \\d+ ssh2
.br
context=SUPPRESS_IP_$1
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from ([\\d.]+) port \\d+ ssh2
.br
desc=Three SSH login failures within 1m for user $1 from $2
.br
action=pipe '%t: %s' /bin/mail root@localhost; \\
       create SUPPRESS_IP_$2 3600
.br
window=60
.br
thresh=3
.PP
The first rule filters out SSH login failure events for an already reported
source IP address, so that they will not be matched
against the second rule during 3600 seconds after sending an e-mail warning.
.SS "CALENDAR RULE"
The Calendar rule supports the following fields.
.TP 
.I type
fixed to Calendar (value is case insensitive).
.TP 
.I time
time specification.
.TP 
.IR context " (optional)"
context expression.
.TP 
.I desc
operation description string.
.TP 
.I action
action list.
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B Calendar
rule was designed for executing actions at specific times. Unlike all
other rules, this rule reacts only to the system clock, ignoring other
input. 
The Calendar rule executes the action list given with the
.I action
field if the current time matches all conditions of the time specification 
given with the
.I time 
field. The action list is executed only once for any matching minute.
.PP
The rule employs a time specification which closely resembles the
.BR crontab (1)
style, but there are some subtle differences.
The time specification consists of five or six conditions separated
by whitespace. The first condition matches minutes 
(allowed values are 0-59), the second condition matches hours (allowed values
are 0-23), the third condition days (allowed values are 0-31, with 0 denoting
the last day of the month), the fourth condition months (allowed values are
1-12), and the fifth condition weekdays (allowed values are 0-7, with 0 and 7 
denoting Sunday). The sixth condition is optional and matches years (allowed
values are 0-99 which denote the last two digits of the year).
.PP
Asterisks (*), ranges of numbers (e.g., 8-11), and lists (e.g., 
2,5,7-9) are allowed as conditions. Asterisks and ranges may be augmented
with step values (e.g., 47-55/2 means 47,49,51,53,55). 
.PP
Note that unlike
.BR crontab (1)
time specification, the day and weekday conditions are *not* joined with 
logical OR, but rather with logical AND.
Therefore, 0 1 25-31 10 7 means 1AM on last Sunday in October. 
On the other hand, with
.BR crontab (1)
the same specification means 1AM in every last seven days or every Sunday
in October.
.PP
Also, unlike some versions of
.BR cron (8),
SEC is not restricted to take action only during the first second of
the current minute. For example, if SEC is started at the 22th second
of a minute, the wildcard condition produces a match for this minute.
As another example, if the time specification matches the current minute
but the context expression evaluates FALSE during the first half of the
minute, the Calendar rule will execute the action list in the middle of
this minute when the expression value becomes TRUE.
.PP
Note that the Calendar rule does not start event correlation operations, 
and the
.I desc
field is merely used for setting the %s action list variable.
.PP
.B Examples:
.PP
type=Calendar
.br
time=0 2 25-31 3,12 6
.br
desc=Check if backup is done on last Saturday of Q1 and Q4
.br
action=event WAITING_FOR_BACKUP
.PP
type=Calendar
.br
time=0 2 24-30 6,9 6
.br
desc=Check if backup is done on last Saturday of Q2 and Q3
.br
action=event WAITING_FOR_BACKUP
.PP
type=PairWithWindow
.br
ptype=SubStr
.br
pattern=WAITING_FOR_BACKUP
.br
desc=Quarterly backup not completed on time!
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
ptype2=SubStr
.br
pattern2=BACKUP READY
.br
desc2=Quarterly backup successfully completed
.br
action2=none
.br
window=1800
.PP
The first two rules create a synthetic event WAITING_FOR_BACKUP at 2AM
on last Saturday of March, June, September and December.
The third rule matches this event and starts an event correlation operation
which waits for the BACKUP READY event for 1800 seconds. If this event
has not arrived by 2:30AM, the operation sends an e-mail warning to
root@localhost.
.SS "JUMP RULE"
The Jump rule supports the following fields.
Note that match variables may be used in the
.I context
field. They may also be used in the
.I cfset
field, provided that the 
.I constset 
field is set to No.
.TP 
.I type
fixed to Jump (value is case insensitive).
.TP 
.IR continue " (optional)"
TakeNext, DontCont, EndMatch or GoTo <label> (apart from <label>, 
values are case insensitive).
.TP 
.I ptype
pattern type (value is case insensitive).
.TP 
.I pattern
pattern.
.TP 
.IR varmap " (optional)"
variable map.
.TP 
.IR context " (optional)"
context expression.
.TP
.IR cfset " (optional)"
configuration file set names that are separated by whitespace.
.TP
.IR constset " (optional)"
Yes or No (values are case insensitive, default is Yes). 
.TP
.IR desc " (optional)"
string for describing the rule.
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B Jump
rule submits matching events to specific ruleset(s) for 
further processing. If the event matches the rule, 
SEC continues the search for matching rules in configuration file 
set(s) given with the 
.I cfset
field. Rules from every file are tried in the order of their
appearance in the file.
Configuration file sets can be created from Options rules with the
.I joincfset
field, with each set containing at least one configuration file.
If more that one set name is given with
.IR cfset , 
sets are processed from left to right;
a matching rule in one set doesn't prevent SEC from processing the following 
sets. If the 
.I constset
field is set to Yes, set names are assumed to be constants and will not
be searched for match variables at runtime.
.PP
If the
.I cfset
field is not present and the
.I continue
field is set to GoTo, the Jump rule can be used for skipping rules inside
the current configuration file. If both
.I cfset
and
.I continue
are not present (or 
.I continue
is set to DontCont), Jump is identical to Suppress rule.
Finally, if
.I cfset
is not present and
.I continue
is set to EndMatch, processing of the matching event ends (i.e., 
no further rules from any of the configuration files will be tried).
.PP
Note that the Jump rule does not start event correlation operations, 
and the optional
.I desc
field is merely used for describing the rule.
.PP
.B Examples:
.PP
type=Jump
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]:
.br
cfset=sshd-rules auth-rules
.PP
When an sshd syslog message appears in input, rules from configuration files
of the set
.B sshd\-rules
are first used for matching the message, and then rules from the configuration
file set
.B auth\-rules
are tried.
.SS "OPTIONS RULE"
The Options rule supports the following fields.
.TP 
.I type
fixed to Options (value is case insensitive).
.TP 
.IR joincfset " (optional)"
configuration file set names that are separated by whitespace.
.TP 
.IR procallin " (optional)"
Yes or No (values are case insensitive, default is Yes). 
.TP 
.IR rem " (optional, may appear more than once)"
remarks and comments.
.PP
The
.B Options
rule sets processing options for the ruleset in the current
configuration file. If more than one Options rule is present in the 
configuration file, the last instance overrides all previous ones. Note
that the Options rule is only processed when SEC (re)starts and reads in the
configuration file. 
Since this rule is not applied at runtime, it can never match
events, react to the system clock, or start event correlation operations.
.PP
The
.I joincfset
field lists the names of one or more configuration file sets, 
and the current configuration file will be added to each set.
If a set doesn't exist, it will be created and the current
configuration file becomes its first member.
If the 
.I procallin
field is set to No, the rules from the configuration file will be
used for matching input from Jump rules only.
.PP
.B Examples:
.PP
The following rule adds the current configuration file to the set
.B sshd\-rules
which is used for matching input from Jump rules only:
.PP
type=Options
.br
joincfset=sshd-rules
.br
procallin=no
.PP
The following rule adds the current configuration file to sets
.B linux
and
.B solaris
which are used for matching all input:
.PP
type=Options
.br
joincfset=linux solaris
.SH EVENT CORRELATION OPERATIONS
Event correlation operations are dynamic entities created by rules.
After creating an operation, the rule also feeds the operation with events
that need to be correlated. Since each rule can create and feed many operations
which are running simultaneously, each operation needs a unique ID.
.PP
In order to identify event correlation operations,
SEC assigns an ID to every operation that is composed from the configuration 
file name, the rule number, and the operation description string
(defined by the
.I desc
field of the rule).
If there are N rules in the configuration file (excluding Options rules), 
the rule numbers belong to the range 0..N-1, and the number of the k-th rule 
is k-1. 
Since each Options rule is only processed when SEC reads in the configuration 
file and is not applied at runtime, the Options rules will not receive rule 
numbers.
Note that since the configuration file name and rule number are part of 
the operation ID, different rules can have identical
.I desc
fields without a danger of a clash between operations.
.PP
For example, if the configuration file /etc/sec/my.conf contains only one rule
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=user (\\S+) login failure on (\\S+)
.br
desc=Repeated login failures for user $1 on $2
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
window=60
.br
thresh=3
.PP
then the number of this rule is 0.
When this rule matches an input event "user admin login failure on tty1", 
the 
.I desc
field yields an operation description string
.IR "Repeated login failures for user admin on tty1" , 
and the event will be directed for further processing to the operation with 
the following ID:
.PP
/etc/sec/my.conf | 0 | Repeated login failures for user admin on tty1
.PP
If the operation for this ID does not exist, the rule will create it.
The newly created operation has its event counter initialized to 1, and it
expects to receive two additional "user admin login failure on tty1" events
from the rule within the following 60 seconds. If the operation receives
such an event, its event counter is incremented, and if the counter reaches
the value of 3, a warning e-mail is sent to root@localhost. 
.PP
By tuning the
.I desc
field of the rule, the scope of individual event correlation operations can 
be changed.
For instance, if the following events occur within 10 seconds
.PP
user admin login failure on tty1
.br
user admin login failure on tty5
.br
user admin login failure on tty2
.PP
the above rule starts three event correlation operations.
However, if the
.I desc
field of the rule is changed to 
.IR "Repeated login failures for user $1" , 
these events are processed by the *same* event correlation operation 
(the operation sends a warning e-mail to root@localhost when it receives
the third event).
.PP
Since rules from the same configuration file are matched against input in 
the order they are given, the rule ordering influences the creation and
feeding of event correlation operations. Suppose the configuration file
/etc/sec/my.conf contains the following rules:
.PP
type=Suppress
.br
ptype=TValue
.br
pattern=TRUE
.br
context=MYCONTEXT 
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=user (\\S+) login failure on (\\S+)
.br
desc=Repeated login failures for user $1 on $2
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
window=60
.br
thresh=3
.PP
The second rule is able to create and feed event correlation operations
as long as the context MYCONTEXT does not exist. However, after MYCONTEXT
has been created, no input event will reach the second rule, and the rule
is thus unable to create new operations and feed existing ones with events.
.PP
Note that Pair and PairWithWindow rules can feed the same event to several
operations. Suppose the configuration file /etc/sec/my2.conf contains 
the following rules:
.PP
type=Suppress
.br
ptype=SubStr
.br
pattern=test
.PP
type=Pair
.br
ptype=RegExp
.br
pattern=database (\\S+) down
.br
desc=Database $1 is down
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
ptype2=RegExp
.br
pattern2=database $1 up|all databases up
.br
desc2=Database %1 is up
.br
action2=pipe '%t: %s' /bin/mail root@localhost
.br
window=86400
.PP
Since the following input events don't contain the substring "test"
.PP
database mydb1 down
.br
database mydb2 down
.br
database mydb3 down
.PP
they are matched by the second rule of type Pair which creates three event 
correlation operations. Each operation is running for one particular 
database name, and the operations have the following IDs:
.PP
/etc/sec/my2.conf | 1 | Database mydb1 is down
.br
/etc/sec/my2.conf | 1 | Database mydb2 is down
.br
/etc/sec/my2.conf | 1 | Database mydb3 is down
.PP
Each newly created operation sends an e-mail notification to root@localhost
about the "database down" condition, and will then wait for 86400 seconds
(24 hours) for either of the following messages:  
.br
(a) "database up" message for the given database, 
.br
(b) "all databases up" message.
.PP
The operation with the ID 
.PP
/etc/sec/my2.conf | 1 | Database mydb1 is down
.PP
uses the following regular expression for matching expected messages:
.PP
database mydb1 up|all databases up
.PP
The operation with the ID
.PP
/etc/sec/my2.conf | 1 | Database mydb2 is down
.PP
employs the following regular expression for matching expected messages:
.PP
database mydb2 up|all databases up
.PP
Finally, the operation with the ID
.PP
/etc/sec/my2.conf | 1 | Database mydb3 is down
.PP
uses the following regular expression:
.PP
database mydb3 up|all databases up
.PP
If the following input events appear after 10 minutes
.PP
database test up
.br
admin logged in
.br
database mydb3 up
.br
all databases up
.PP
the first event "database test up" matches the first rule (Suppress)
which does not pass the event further to the second rule (Pair).
However, all following events reach the Pair rule. 
Since the messages don't match the
.I pattern
field of the rule, the rule feeds them to all currently existing operations 
it has created, so that the operations can match these events with their 
regular expressions.
Because regular expressions of all three operations don't match 
the event "admin logged in", the operations will continue to run.
In the case of the "database mydb3 up" event, the regular expression 
of the operation 
.PP
/etc/sec/my2.conf | 1 | Database mydb3 is down
.PP
produces a match. Therefore, the operation will send 
the e-mail notification "Database mydb3 is up" to root@localhost and 
terminate.
However, the following event "all databases up" matches the regular 
expressions of two remaining operations. As a result, the operations will 
send e-mail notifications "Database mydb1 is up" and "Database mydb2 is up" 
to root@localhost and terminate.
.PP
Each operation has an event correlation window which defines its
scope in time. The size of the
window is defined by the
.I window*
field, and the beginning of the window can be obtained with the
.I getwpos
action. SingleWithThreshold, SingleWith2Thresholds and
EventGroup operations can slide its window forward during event processing, 
while for all operations the window can also be moved explicitly with the
.I setwpos
action. Also, with the
.I reset
action event correlation operations can be terminated. Note that
.IR getwpos ,
.IR setwpos ,
and
.I reset
actions only work for operations started by the rules from the same 
configuration file.
.PP
For example, consider the configuration file /etc/sec/sshd.rules that 
contains the following rules:
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from [\\d.]+ port \\d+ ssh2
.br
desc=Three SSH login failures within 1m for user $1
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
window=60
.br
thresh=3
.PP
type=Single
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Accepted .+ for (\\S+) from [\\d.]+ port \\d+ ssh2
.br
desc=SSH login successful for user $1
.br
action=reset -1 Three SSH login failures within 1m for user $1
.PP
Suppose the following events are generated by an SSH daemon, and each
event timestamp reflects the time SEC observes the event:
.PP
Dec 29 15:00:03 test sshd[14129]: Failed password for risto from 10.1.2.7 port 31312 ssh2
.br
Dec 29 15:00:08 test sshd[14129]: Failed password for risto from 10.1.2.7 port 31312 ssh2
.br
Dec 29 15:00:17 test sshd[14129]: Accepted password for risto from 10.1.2.7 port 31312 ssh2
.br
Dec 29 15:00:52 test sshd[14142]: Failed password for risto from 10.1.1.2 port 17721 ssh2
.PP
The first event at 15:00:03 starts an event correlation operation with the ID
.PP
/etc/sec/sshd.rules | 0 | Three SSH login failures within 1m for user risto
.PP
However, when the third event occurs at 15:00:17, the second rule matches
it and terminates the operation with the action
.PP
reset -1 Three SSH login failures within 1m for user risto
.PP
The -1 parameter of
.I reset
restricts the action to operations started by the previous rule 
(i.e., the first rule that has a number 0), while the
.I Three SSH login failures within 1m for user risto
parameter refers to the operation description string. Together with 
the current configuration file name (/etc/sec/sshd.rules), 
the parameters yield the operation ID
.PP
/etc/sec/sshd.rules | 0 | Three SSH login failures within 1m for user risto
.PP
(If the operation with the given ID would not exist,
.I reset
would perform no operation.)
.PP
As a consequence, the fourth event at 15:00:52 starts another operation with
the same ID as the terminated operation had. Without the second rule, 
the operation that was started at 15:00:03 would not be terminated, 
and the appearance of the fourth event would trigger a warning e-mail from 
that operation.
.SH INPUT PROCESSING AND TIMING
SEC processes input data iteratively by reading one line at each iteration,
writing this line into a relevant input buffer, and matching the content
of the updated buffer with rules from configuration files.
If during the matching process an action list is executed which creates new
input events (e.g., through the
.I event
action), they are *not* written to buffer(s) immediately,
but rather consumed at following iterations.
.PP
Note that when both synthetic events and regular input are available for 
processing, synthetic events are always consumed first.
When all synthetic events have been consumed iteratively, 
SEC will start processing new data from input files.
.PP
With the
.B \-\-jointbuf
option, SEC employs a joint input buffer for all input sources which holds
N last input lines (the value of N can be set with the
.B \-\-bufsize
option). Updating the input buffer means that the new line becomes the first
element of the buffer, while the last element (the oldest line) is removed 
from the end of the buffer. 
With the 
.B \-\-nojointbuf
option, SEC maintains a buffer of N lines for each input file, and 
if the input line comes from file F, the buffer of F is updated as described
previously.
There is also a separate buffer for synthetic and internal events.
.PP
Suppose SEC is started with the following command line
.PP
/usr/bin/sec --conf=/etc/sec/test-multiline.conf --jointbuf \\
             --input=/var/log/prog1.log --input=/var/log/prog2.log
.PP
and the configuration file /etc/sec/test-multiline.conf has the following
content:
.PP
type=Single
.br
rem=this rule matches two consecutive lines where the first \\
    line contains "test1" and the second line "test2", and \\
    writes the matching lines to standard output
.br
ptype=RegExp2
.br
pattern=test1.*\\n.*test2
.br
desc=two consecutive test lines
.br
action=write - $0
.PP
When the following lines appear in input files /var/log/prog1.log and
/var/log/prog2.log
.PP
Dec 31 12:33:12 test prog1: test1 (file /var/log/prog1.log)
.br
Dec 31 12:34:09 test prog2: test1 (file /var/log/prog2.log)
.br
Dec 31 12:39:35 test prog1: test2 (file /var/log/prog1.log)
.br
Dec 31 12:41:53 test prog2: test2 (file /var/log/prog2.log)
.PP
they are stored in a common input buffer. Therefore, rule fires after
the third event has appeared, and writes the following
lines to standard output:
.PP
Dec 31 12:34:09 test prog2: test1 (file /var/log/prog2.log)
.br
Dec 31 12:39:35 test prog1: test2 (file /var/log/prog1.log)
.PP
However, if SEC is started with the 
.B \-\-nojointbuf 
option, separate input buffers are set up for /var/log/prog1.log and
/var/log/prog2.log. 
Therefore, the rule fires after the third event has occurred,
and writes the following lines to standard output:
.PP
Dec 31 12:33:12 test prog1: test1 (file /var/log/prog1.log)
.br
Dec 31 12:39:35 test prog1: test2 (file /var/log/prog1.log)
.PP
The rule also fires after the fourth event has occurred,
producing the following output:
.PP
Dec 31 12:34:09 test prog2: test1 (file /var/log/prog2.log)
.br
Dec 31 12:41:53 test prog2: test2 (file /var/log/prog2.log)
.PP
The content of input buffers can be modified with the
.I rewrite
action, and modifications become visible immediately during 
ongoing event processing iteration.
Suppose SEC is started with the following command line
.PP
/usr/bin/sec --conf=/etc/sec/test-rewrite.conf \\
             --input=- --nojointbuf
.PP
and the configuration file /etc/sec/test-rewrite.conf has the following
content:
.PP
type=Single
.br
rem=this rule matches two consecutive lines where the first \\
    line contains "test1" and the second line "test2", and \\
    joins these lines in the input buffer
.br
ptype=RegExp2
.br
pattern=^(.*test1.*)\\n(.*test2.*)$
.br
continue=TakeNext
.br
desc=join two test lines
.br
action=rewrite 2 Joined $1 and $2
.PP
type=Single
.br
rem=this rule matches a line which begins with "Joined", \\
    and writes this line to standard output
.br
ptype=RegExp
.br
pattern=^Joined
.br
desc=output joined lines
.br
action=write - $0
.PP
When the following two lines appear in standard input
.PP
This is a test1
.br
This is a test2
.PP
they are matched by the first rule which uses the
.I rewrite 
action for replacing those two lines in the input buffer with a new content.
The last line in the input buffer ("This is a test2") is replaced with
"Joined This is a test1 and This is a test2", while the previous line in
the input buffer ("This is a test1") is replaced with an empty string.
Since the rule contains
.I continue=TakeNext
statement, the matching process will continue from the following rule.
This rule matches the last line in the input buffer if it begins 
with "Joined", and writes the line to standard output, producing
.PP
Joined This is a test1 and This is a test2
.PP
After each event processing iteration, the pattern match cache is cleared. 
In other words, if a match is cached with the rule
.I varmap*
field, it is available during ongoing iteration only. 
Note that results from a successful pattern matching are also cached when 
the subsequent context expression evaluation yields FALSE. 
This allows for reusing results from partial rule matches.
For example, the following rule creates the cache entry "ssh_failed_login" for
any SSH failed login event, even if the context ALERTING_ON does not exist:
.PP
type=Single
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (\\S+) from ([\\d.]+) port \\d+ ssh2
.br
varmap=ssh_failed_login; user=1; ip=2
.br
context=ALERTING_ON
.br
desc=SSH login failure for user $1 from $2
.br
action=pipe '%s' /bin/mail -s 'SSH login alert' root@localhost
.PP
However, provided the context expression does not contain match variables,
enclosing the expression in square brackets (e.g., [ALERTING_ON])
forces its evaluation before the pattern matching, and will thus prevent the
matching and the creation of the cache entry if the evaluation yields FALSE.
.PP
Rules from the same configuration file are matched against the buffer content
in the order they are given in that file.
When multiple configuration files have been specified, rule sequences from 
all files are matched against the buffer content (unless specified otherwise 
with Options rules).
The matching order is determined by the order of configuration files 
in SEC command line.
For example, if the Perl
.BR glob ()
function returns filenames in ascending ASCII order, and configuration
files /home/risto/A.conf, /home/risto/B.conf2, and /home/risto/C.conf
are specified with
.B \-\-conf=/home/risto/*.conf \-\-conf=/home/risto/*.conf2
in SEC command line,
then SEC first matches the input against the rule sequence from A.conf, then
from C.conf, and finally from B.conf2.
Also, note that even if A.conf contains a Suppress rule for 
a particular event, the event is still processed by rulesets in C.conf and 
B.conf2. However, note that 
.BR glob ()
might return file names in different order if locale settings change.
If you want to enforce a fixed order for configuration file 
application in a portable way, it is recommended to create a unique set
for each file with the Options rule, and employ the Jump rule for defining
the processing order for sets, e.g.:
.PP
# This rule appears in A.conf
.br
type=Options
.br
joincfset=FileA
.br
procallin=no
.PP
# This rule appears in B.conf2
.br
type=Options
.br
joincfset=FileB
.br
procallin=no
.PP
# This rule appears in C.conf
.br
type=Options
.br
joincfset=FileC
.br
procallin=no
.PP
# This rule appears in main.conf
.br
type=Jump
.br
ptype=TValue
.br
pattern=TRUE
.br
cfset=FileA FileC FileB
.PP
After the relevant input buffer has been updated and its content has been 
matched by the rules, SEC handles caught signals and checks the status of 
child processes.
When the timeout specified with the
.B \-\-cleantime
option has expired, SEC also checks the status of contexts and event 
correlation operations. Therefore, relatively small values should be
specified with the 
.B \-\-cleantime
option, in order to retain the accuracy of the event correlation process.
If the 
.B \-\-cleantime
option is set to 0, SEC checks event correlation operations and contexts
after processing every input line, but this consumes more CPU time.
If the
.B \-\-poll\-timeout
option value exceeds the value given with
.BR \-\-cleantime ,
the 
.B \-\-poll\-timeout
option value takes precedence (i.e., sleeps after unsuccessful polls will 
not be shortened).
.PP
Finally, note that apart from the sleeps after unsuccessful polls, SEC 
measures all time intervals and occurrence times in seconds, and always uses 
the
.BR time (2)
system call for obtaining the current time. Also, for input event occurrence
time SEC always uses the time it observed the event, *not* the timestamp 
extracted from the event.
.SH INTERNAL EVENTS AND CONTEXTS
In the action list of a context, the context can also be referred
with the internal context name _THIS. The name _THIS is created and 
deleted dynamically by SEC and it points to the context only during its action 
list execution. 
This feature is useful when the context has had several names during its 
lifetime (created with the
.I alias
action), and it is hard to determine which names exist when the context 
expires. For example, if the context is created with 
.I create A 60 (report A /bin/mail root) 
which is immediately followed by 
.I alias A B
and
.IR "unalias A" ,
the 
.I report
action will fail since the name A no longer refers to the context. 
However, replacing the first action with
.I create A 60 (report _THIS /bin/mail root)
will produce the correct result.
.PP
If the
.B \-\-intevents
command line option is given, SEC will generate internal events when
it is started up, when it receives certain signals, and when it terminates
normally. Inside SEC, internal event is treated as if it was a line that 
was read from a SEC input file.
Specific rules can be written to match internal events, in order to take some 
action (e.g., start an external event correlation module with 
.I spawn
when SEC starts up). The following internal events are
supported:
.PP
SEC_STARTUP - generated when SEC is started (this event will always be 
the first event that SEC sees)
.PP
SEC_PRE_RESTART - generated before processing of the
.B SIGHUP
signal (this event will be the last event that SEC sees before clearing 
all internal data structures and reloading its configuration)
.PP
SEC_RESTART - generated after processing of the
.B SIGHUP
signal (this event will be the first event that SEC sees after clearing 
all internal data structures and reloading its configuration)
.PP
SEC_PRE_SOFTRESTART - generated before processing of the
.B SIGABRT
signal (this event will be the last event that SEC sees before reloading
its configuration)
.PP
SEC_SOFTRESTART - generated after processing of the
.B SIGABRT
signal (this event will be the first event that SEC sees after reloading
its configuration)
.PP
SEC_PRE_LOGROTATE - generated before processing of the
.B SIGUSR2
signal (this event will be the last event that SEC sees before reopening 
its log file and closing its outputs)
.PP
SEC_LOGROTATE - generated after processing of the
.B SIGUSR2
signal (this event will be the first event that SEC sees after reopening 
its log file and closing its outputs)
.PP
SEC_SHUTDOWN - generated when SEC receives the
.B SIGTERM
signal, or when SEC reaches all EOFs of input files after being started with 
the
.B \-\-notail
option. With the
.B \-\-childterm
option, SEC sleeps for 3 seconds after generating SEC_SHUTDOWN event, and then 
sends 
.B SIGTERM 
to its child processes (if a child process was triggered by 
SEC_SHUTDOWN, this delay leaves the process enough time for setting a signal 
handler for 
.BR SIGTERM ).
.PP
Before generating an internal event, SEC sets up a context named 
SEC_INTERNAL_EVENT, in order to disambiguate internal events from
regular input.
The SEC_INTERNAL_EVENT context is deleted immediately after the
internal event has been matched against all rules.
.PP
If the
.B \-\-intcontexts
command line option is given, or there is an
.B \-\-input
option with a context specified, SEC creates an internal context each time
it reads a line from an input file or a synthetic event.
The internal context is deleted immediately after the line has
been matched against all rules. For all input files that have the context
name explicitly set with
.BR \-\-input=<file_pattern>=<context> ,
the name of the internal context is <context>. If the line was read from 
the input file <filename> for which there is no context name set, the name 
of the internal context is _FILE_EVENT_<filename>. 
For synthetic events, the name of the internal context defaults 
to _INTERNAL_EVENT, but 
.I cspawn
and
.I cevent
actions can be used for generating synthetic events with custom internal
context names. This allows for writing rules that match data from one 
particular input source only. For example, the rule
.PP
type=Suppress
.br
ptype=TValue
.br
pattern=TRUE
.br
context=[!_FILE_EVENT_/dev/logpipe]
.PP
passes only the lines that were read from /dev/logpipe, and also synthetic
events that were generated with the _FILE_EVENT_/dev/logpipe internal
context (e.g., with the action
.IR "cevent _FILE_EVENT_/dev/logpipe 0 This is a test event" ).
As another example, if SEC has been started with the command line
.PP
/usr/bin/sec --intevents --intcontexts --conf=/etc/sec/my.conf \\
             --input=/var/log/messages=MESSAGES \\
             --input=/var/log/secure=SECURE \\
             --input=/var/log/cron=CRON 
.PP
and the rule file /etc/sec/my.conf contains the following rules
.PP
type=Single
.br
ptype=RegExp
.br
pattern=^(?:SEC_STARTUP|SEC_RESTART)$
.br
context=[SEC_INTERNAL_EVENT]
.br
desc=listen on 10514/tcp for incoming events 
.br
action=cspawn MESSAGES /usr/bin/nc -l -k 10514
.PP
type=Single
.br
ptype=RegExp
.br
pattern=.
.br
context=[MESSAGES]
.br
desc=echo everything from 10514/tcp and /var/log/messages
.br
action=write - $0
.PP
then SEC will receive input lines from the log files /var/log/messages, 
/var/log/secure, and /var/log/cron, and will also run /usr/bin/nc for
receiving input lines from the port 10514/tcp. All input lines from
/var/log/messages and 10514/tcp are matched by the second rule and
written to standard output.
.SH CHILD PROCESSES
The SingleWithScript rule and
.IR shellcmd ,
.IR spawn ,
.IR cspawn ,
.IR cmdexec ,
.IR spawnexec ,
.IR cspawnexec ,
.IR pipe ,
.IR pipeexec ,
.IR report ,
and
.I reportexec
actions fork a child process for executing an external program. 
For the SingleWithScript rule with 
.I shell=yes
setting and for
.IR shellcmd ,
.IR spawn ,
.IR cspawn ,
.IR pipe ,
and
.I report
actions, the following rule applies --
if the program command line contains shell metacharacters, the command
line is first parsed by the shell which then starts the program.
For the SingleWithScript rule with 
.I shell=no
setting and for
.IR cmdexec ,
.IR spawnexec ,
.IR cspawnexec ,
.IR pipeexec ,
and
.I reportexec
actions, the program command line is not parsed by shell, 
even if shell metacharacters are present in the command line.
.PP
Disabling shell parsing for command lines can be useful for avoiding unwanted
side effects. For example, consider the following badly written rule for
sending an e-mail to a local user if 10 SSH login failures have been observed
for this user from the same IP address during 300 seconds:
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=sshd\\[\\d+\\]: Failed .+ for (.+) from ([\\d.]+) port \\d+ ssh2
.br
desc=Failed SSH logins for user $1 from $2
.br
action=pipe 'Failed SSH logins from $2' /bin/mail -s alert $1
.br
window=300
.br
thresh=10
.PP
Unfortunately, the above rule allows for the execution of arbitrary command 
lines with the privileges of the SEC process. 
For example, consider the following malicious command line for providing
fake input events for the rule:
.PP
logger -p authpriv.info -t sshd -i 'Failed password for `/usr/bin/touch /tmp/test` from 127.0.0.1 port 12345 ssh2'
.PP
When this command line is repeatedly executed, the attacker is able to trigger 
the execution of the command line
.IR "/bin/mail -s alert `/usr/bin/touch /tmp/test`" .
However, this command line is parsed by shell that triggers the execution
of the command line specified by the attacker:
.IR "/usr/bin/touch /tmp/test" .
For fixing this issue, the
.I pipe
action can be replaced with
.I pipeexec
which will disable the shell parsing:
.PP
action=pipeexec 'Failed SSH logins from $2' /bin/mail -s alert $1
.PP
However, when using that approach, you *must* make sure that the data passed
to an external program is handled without any unexpected side effects.
.PP
As another workaround, the regular expression pattern of the rule can be 
modified to match user names that do not contain shell metacharacters, 
for example:
.PP
pattern=sshd\\[\\d+\\]: Failed .+ for ([\\w.-]+) from ([\\d.]+) port \\d+ ssh2
.PP
SEC communicates with its child processes through pipes (created with the 
.BR pipe (2) 
system call). 
When the child process is at the read end of the pipe, data have to be written
to the pipe in blocking mode which ensures reliable data transmission. 
In order to avoid being blocked, SEC forks another SEC process for writing 
data to the pipe reliably. The newly created SEC process will then fork
the child process, managing the child process on behalf of the main 
SEC process (i.e., the main SEC process is the grandparent process for 
the child). For example, if the SEC process that manages the child receives
the
.B SIGTERM
signal, the signal will be forwarded to the child process, and when the child
process terminates, its exit code will be reported to the main SEC process.
.PP
After forking an external program, SEC continues immediately, and checks
the program status periodically until the program exits. The running time of 
a child process is not limited in any way. With the
.B \-\-childterm
option, SEC sends the
.B SIGTERM 
signal to all child processes when it terminates.
If some special exit procedures need to be accomplished in the child process
(or the child wishes to ignore 
.BR SIGTERM ), 
then the child must install a handler for the 
.B SIGTERM 
signal. 
Note that if the program command line is parsed by shell,
the parsing shell will run as a child process of SEC and the parent 
process of the program. Therefore, the 
.B SIGTERM
signal will be sent to the shell, *not* the program. In order to avoid this,
the shell's builtin
.I exec
command can be used (see
.BR sh (1)
for more information) which replaces the shell with the program
without forking a new process, e.g., 
.PP
action=spawn exec /usr/local/bin/myscript.pl 2>/var/log/myscript.log
.PP
Note that if an action list includes two actions which fork
external programs, the execution order these programs is not determined
by the order of actions in the list, since both programs are running
asynchronously.
In order to address this issue, the execution order must be specified
explicitly (e.g., instead of writing
.IR "action=shellcmd cmd1; shellcmd cmd2" ,
use the shell && operator and write
.IR "action=shellcmd cmd1 && cmd2" ).
.PP
Sometimes it is desirable to start an external program and provide it with
data from several rules. In order to create such setup, named pipes can be 
harnessed. For example, if /var/log/pipe is a named pipe, then
.PP
action=shellcmd /usr/bin/logger -f /var/log/pipe -p user.notice
.PP
starts the /usr/bin/logger utility which sends all lines read from 
/var/log/pipe to the local syslog daemon with the "user" facility and "notice" 
level. In order to feed events to /usr/bin/logger, the
.I write
action can be used (e.g.,
.IR "write /var/log/pipe This is my event" ).
Although SEC keeps the named pipe open across different
.I write
actions, the pipe will be closed on the reception of 
.BR SIGHUP , 
.B SIGABRT 
and 
.B SIGUSR2 
signals. 
Since many UNIX tools terminate on receiving EOF from standard input, 
they need restarting after such signals have arrived. For this purpose, the
.B --intevents
option and SEC internal events can be used. For example, the following rule 
starts the /usr/bin/logger utility at SEC startup, and also restarts it after 
the reception of relevant signals:
.PP
type=Single
.br
ptype=RegExp
.br
pattern=^(?:SEC_STARTUP|SEC_RESTART|SEC_SOFTRESTART|SEC_LOGROTATE)$
.br
context=SEC_INTERNAL_EVENT
.br
desc=start the logger tool
.br
action=free %emptystring; owritecl /var/log/pipe %emptystring; \\
       shellcmd /usr/bin/logger -f /var/log/pipe -p user.notice
.PP
Note that if /var/log/pipe is never opened for writing by a
.I write
action, /usr/bin/logger will never see EOF and will thus not terminate. The
.I owritecl
action opens and closes /var/log/pipe without writing any bytes, in order 
to ensure the presence of EOF in such cases. This allows any previous 
/usr/bin/logger process to terminate before the new process is started.
.SH PERL INTEGRATION
SEC supports patterns, context expressions, and actions 
which involve calls to the Perl
.BR eval ()
function or the execution of precompiled Perl code. The use of Perl code
in SEC patterns and context expressions allows for creating proper match 
conditions for scenarios which can't be handled by a simple regular
expression match. For example, consider the following iptables syslog events:
.PP
May 27 10:00:15 box1 kernel: iptables: IN=eth0 OUT= MAC=08:00:27:be:9e:2f:00:10:db:ff:20:03:08:00 SRC=10.6.4.14 DST=10.1.8.2 LEN=84 TOS=0x00 PREC=0x00 TTL=251 ID=61426 PROTO=ICMP TYPE=8 CODE=0 ID=11670 SEQ=2
.br
May 27 10:02:22 box1 kernel: iptables: IN=eth0 OUT= MAC=08:00:27:be:9e:2f:00:10:db:ff:20:03:08:00 SRC=10.6.4.14 DST=10.1.8.2 LEN=52 TOS=0x00 PREC=0x00 TTL=60 ID=61441 DF PROTO=TCP SPT=53125 DPT=23 WINDOW=49640 RES=0x00 SYN URGP=0
.PP
Depending on the protocol and the nature of the traffic, events can have 
a wide variety of fields, and parsing out all event data with one regular 
expression is infeasible. For addressing this issue, a PerlFunc pattern can 
be used which creates match variables from all fields of the matching event, 
stores them in one Perl hash, and returns a reference to this hash. Outside 
the PerlFunc pattern, match variables are initialized from the key-value
pairs in the returned hash.
Suppose the following Jump rule with a PerlFunc pattern is defined in 
the main.rules rule file:
.PP
type=Jump
.br
ptype=PerlFunc
.br
pattern=sub { my(%var); my($line) = $_[0]; \\
        if ($line !~ /kernel: iptables:/g) { return 0; } \\
        while ($line =~ /\\G\\s*([A-Z]+)(?:=(\\S*))?/g) { \\
          $var{$1} = defined($2)?$2:1; \\
        } return \\%var; }
.br
varmap=IPTABLES
.br
desc=parse iptables event
.br
cfset=iptables
.PP
For example, if the iptables event contains the fields SRC=10.6.4.14,
DST=10.1.8.2 and SYN, the above PerlFunc pattern sets up match variable 
$+{SRC} which holds 10.6.4.14, match variable $+{DST} which holds 10.1.8.2,
and match variable $+{SYN} which holds 1.
The Jump rule caches all created match variables under the name IPTABLES, 
and submits the matching event to 
.B iptables
ruleset for further processing. Suppose the 
.B iptables
ruleset is defined in the iptables.rules rule file:
.PP
type=Options
.br
procallin=no
.br
joincfset=iptables
.PP
type=SingleWithThreshold
.br
ptype=Cached
.br
pattern=IPTABLES
.br
context=IPTABLES :> ( sub { return $_[0]->{"PROTO"} eq "ICMP"; } )
.br
desc=ICMP flood type $+{TYPE} code $+{CODE} from host $+{SRC}
.br
action=logonly
.br
window=10
.br
thresh=100
.PP
type=SingleWithThreshold
.br
ptype=Cached
.br
pattern=IPTABLES
.br
context=IPTABLES :> ( sub { return exists($_[0]->{"SYN"}) && \\
                                   exists($_[0]->{"FIN"}) ; } )
.br
desc=SYN+FIN flood from host $+{SRC}
.br
action=logonly
.br
window=10
.br
thresh=100
.PP
The two SingleWithThreshold rules employ Cached patterns for matching
iptables events by looking up the IPTABLES entry in the pattern match cache
(created by the above Jump rule for each iptables event).
In order to narrow down the match to specific iptables events, the rules 
employ precompiled Perl functions in context expressions. 
The :> operator is used for speeding up the matching, providing the function
with a single parameter which refers to the hash of variable name-value pairs
for the IPTABLES cache entry.
.PP
The first SingleWithThreshold rule logs a warning message if within 10 
seconds 100 iptables events have been observed for ICMP packets with
the same type, code, and source IP address.
The second SingleWithThreshold rule logs a warning message if within 10
seconds 100 iptables events have been observed for TCP packets coming 
from the same host, and having both SYN and FIN flag set in each packet.
.PP
Apart from using action list variables for data sharing between
rules, Perl variables created in Perl code can be employed for the same 
purpose. For example, when SEC has executed the following action
.PP
action=eval %a ($b = 1)
.PP
the variable $b and its value become visible in the following context 
expression 
.PP
context= =(++$b > 10)
.PP
(with that expression one can implement event counting implicitly).
In order to avoid possible clashes with variables inside the SEC
code itself, user-defined Perl code is executed in the main::SEC namespace 
(i.e., inside the special package main::SEC). 
By using the main:: prefix, SEC data structures can be accessed and modified. 
For example, the following rules restore and save contexts with names MY_*
on SEC startup and shutdown, using Perl Storable module for saving and restoring
relevant elements of %main::context_list hash (since the following example
does not handle code references with Storable module, it is assumed that
context action lists do not contain 
.I lcall 
actions):
.PP
type=Single
.br
ptype=SubStr
.br
pattern=SEC_STARTUP
.br
context=SEC_INTERNAL_EVENT
.br
continue=TakeNext
.br
desc=Load the Storable module and terminate if it is not found
.br
action=eval %ret (require Storable); \\
       if %ret ( logonly Storable loaded ) else ( eval %o exit(1) ) 
.PP
type=Single
.br
ptype=SubStr
.br
pattern=SEC_STARTUP
.br
context=SEC_INTERNAL_EVENT
.br
desc=Restore contexts MY_* from /var/lib/sec/SEC_CONTEXTS on startup
.br
action=lcall %ret -> ( sub { my($ref, $context); \\
       $ref = Storable::retrieve("/var/lib/sec/SEC_CONTEXTS"); \\
       foreach $context (keys %{$ref}) { \\
         if ($context =~ /^MY_/) \\
           { $main::context_list{$context} = $ref->{$context}; } } } )
.PP
type=Single
.br
ptype=SubStr
.br
pattern=SEC_SHUTDOWN
.br
context=SEC_INTERNAL_EVENT
.br
desc=Save contexts MY_* into /var/lib/sec/SEC_CONTEXTS on shutdown
.br
action=lcall %ret -> ( sub { my($context, %hash); \\
       foreach $context (keys %main::context_list) { \\
         if ($context =~ /^MY_/) \\
           { $hash{$context} = $main::context_list{$context}; } } \\
       Storable::store(\\%hash, "/var/lib/sec/SEC_CONTEXTS"); } ) 
.PP
However, note that modifying data structures within SEC code is recommended 
only for advanced users who have carefully studied relevant parts of the code. 
.PP
Finally, sometimes larger chunks of Perl code have to be used for event
processing and correlation. However, writing many lines of code directly 
into a rule is cumbersome and may decrease its readability. In such cases
it is recommended to separate the code into a custom Perl module which
is loaded at SEC startup, and use the code through the module interface
(see
.BR perlmod (1)
for further details):
.PP
type=Single
.br
ptype=SubStr
.br
pattern=SEC_STARTUP
.br
context=SEC_INTERNAL_EVENT
.br
desc=Load the SecStuff module
.br
action=eval %ret (require '/usr/local/sec/SecStuff.pm'); \\
       if %ret ( none ) else ( eval %o exit(1) )
.PP
type=Single
.br
ptype=PerlFunc
.br
pattern=sub { return SecStuff::my_match($_[0]); }
.br
desc=event '$0' was matched by my_match()
.br
action=write - %s
.SH EXAMPLES
.SS Example 1 - a ruleset for Cisco events
This section presents an example rulebase for managing Cisco devices.
It is assumed that the managed devices have syslog 
logging enabled, and that all syslog messages are sent to a central host 
and written to log file(s) that are monitored by SEC.
.PP
# Set up contexts NIGHT and WEEKEND for nights 
.br
# and weekends. The context NIGHT has a lifetime
.br
# of 8 hours and the context WEEKEND 2 days
.PP
type=Calendar
.br
time=0 23 * * *
.br
desc=NIGHT
.br
action=create %s 28800
.PP
type=Calendar
.br
time=0 0 * * 6
.br
desc=WEEKEND
.br
action=create %s 172800
.PP
# If a router does not come up within 5 minutes 
.br
# after it was rebooted, generate event 
.br
# "<router> REBOOT FAILURE". The next rule matches 
.br
# this event, checks the router with ping and sends
.br
# a notification if there is no response.
.PP
type=PairWithWindow
.br
ptype=RegExp
.br
pattern=\\s([\\w.-]+) \\d+: %SYS-5-RELOAD
.br
desc=$1 REBOOT FAILURE
.br
action=event %s
.br
ptype2=RegExp
.br
pattern2=\\s$1 \\d+: %SYS-5-RESTART
.br
desc2=%1 successful reboot
.br
action2=logonly
.br
window=300
.PP
type=SingleWithScript
.br
ptype=RegExp
.br
pattern=^([\\w.-]+) REBOOT FAILURE
.br
script=/bin/ping -c 3 -q $1
.br
desc=$1 did not come up after reboot
.br
action=logonly $1 is pingable after reboot
.br
action2=pipe '%t: %s' /bin/mail root@localhost
.PP
# Send a notification if CPU load of a router is too 
.br
# high (two CPUHOG messages are received within 5 
.br
# minutes); send another notification if the load is 
.br 
# normal again (no CPUHOG messages within last 15 
.br
# minutes). Rule is not active at night or weekend.
.PP
type=SingleWith2Thresholds
.br
ptype=RegExp
.br
pattern=\\s([\\w.-]+) \\d+: %SYS-3-CPUHOG
.br
context=!(NIGHT || WEEKEND)
.br
desc=$1 CPU overload
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
window=300
.br
thresh=2
.br
desc2=$1 CPU load normal
.br
action2=pipe '%t: %s' /bin/mail root@localhost
.br
window2=900
.br
thresh2=0
.PP
# If a router interface is in down state for less 
.br
# than 15 seconds, generate event 
.br
# "<router> INTERFACE <interface> SHORT OUTAGE"; 
.br
# otherwise generate event 
.br
# "<router> INTERFACE <interface> DOWN".
.PP
type=PairWithWindow
.br
ptype=RegExp
.br
pattern=\\s([\\w.-]+) \\d+: %LINK-3-UPDOWN: Interface ([\\w.-]+), changed state to down
.br
desc=$1 INTERFACE $2 DOWN
.br
action=event %s
.br
ptype2=RegExp
.br
pattern2=\\s$1 \\d+: %LINK-3-UPDOWN: Interface $2, changed state to up
.br
desc2=%1 INTERFACE %2 SHORT OUTAGE
.br
action2=event %s
.br
window=15
.PP
# If "<router> INTERFACE <interface> DOWN" event is 
.br
# received, send a notification and wait for
.br
# "interface up" event from the same router interface
.br
# for the next 24 hours
.PP
type=Pair
.br
ptype=RegExp
.br
pattern=^([\\w.-]+) INTERFACE ([\\w.-]+) DOWN
.br
desc=$1 interface $2 is down
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
ptype2=RegExp
.br
pattern2=\\s$1 \\d+: %LINK-3-UPDOWN: Interface $2, changed state to up
.br
desc2=%1 interface %2 is up
.br
action2=pipe '%t: %s' /bin/mail root@localhost
.br
window=86400
.PP
# If ten "short outage" events have been observed 
.br
# in the window of 6 hours, send a notification
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=^([\\w.-]+) INTERFACE ([\\w.-]+) SHORT OUTAGE
.br
desc=Interface $2 at node $1 is unstable
.br
action=pipe '%t: %s' /bin/mail root@localhost
.br
window=21600
.br
thresh=10
.SS Example 2 - hierarchically organized rulesets for iptables and sshd events
This section presents an example of hierarchically organized rules for
processing Linux iptables events from /var/log/messages and SSH login events
from /var/log/secure. It is assumed that all rule files reside in the
/etc/sec directory and that the rule hierarchy has two levels. 
The file /etc/sec/main.rules contains first-level Jump rules for matching and
parsing events from input files and submitting them to proper rulesets for 
further processing. All other rule files in the /etc/sec directory contain
second-level rules which receive their input from first-level Jump rules.
Also, the example assumes that SEC is started with the following command line:
.PP
/usr/bin/sec --conf=/etc/sec/*.rules --intcontexts \\
             --input=/var/log/messages --input=/var/log/secure
.PP
#
.br
# the content of /etc/sec/main.rules 
.br
#
.PP
type=Jump
.br
context=[ _FILE_EVENT_/var/log/messages ]
.br
ptype=PerlFunc
.br
pattern=sub { my(%var); my($line) = $_[0]; \\
        if ($line !~ /kernel: iptables:/g) { return 0; } \\
        while ($line =~ /\\G\\s*([A-Z]+)(?:=(\\S*))?/g) { \\
          $var{$1} = defined($2)?$2:1; \\
        } return \\%var; }
.br
varmap=IPTABLES
.br
desc=parse iptables events and direct to relevant ruleset
.br
cfset=iptables
.PP
type=Jump
.br
context=[ _FILE_EVENT_/var/log/secure ]
.br
ptype=RegExp
.br
pattern=sshd\\[(?<pid>\\d+)\\]: (?<status>Accepted|Failed) \\
.br
(?<authmethod>[\\w-]+) for (?<invuser>invalid user )?\\
.br
(?<user>[\\w-]+) from (?<srcip>[\\d.]+) port (?<srcport>\\d+) ssh2$
.br
varmap=SSH_LOGIN
.br
desc=parse SSH login events and direct to relevant ruleset
.br
cfset=ssh-login
.PP
type=Jump
.br
context=[ SSH_EVENT ]
.br
ptype=TValue
.br
pattern=True
.br
desc=direct SSH synthetic events to relevant ruleset
.br
cfset=ssh-events
.PP
#
.br
# the content of /etc/sec/iptables.rules
.br
#
.PP
type=Options
.br
procallin=no
.br
joincfset=iptables
.PP
type=SingleWithThreshold
.br
ptype=Cached
.br
pattern=IPTABLES
.br
context=IPTABLES :> ( sub { return exists($_[0]->{"SYN"}) && \\
                                   exists($_[0]->{"FIN"}) ; } ) \\
        && !SUPPRESS_IP_$+{SRC}
.br
desc=SYN+FIN flood from host $+{SRC}
.br
action=pipe '%t: %s' /bin/mail -s 'iptables alert' root@localhost; \\
       create SUPPRESS_IP_$+{SRC} 3600
.br
window=10
.br
thresh=100
.PP
type=SingleWithThreshold
.br
ptype=Cached
.br
pattern=IPTABLES
.br
context=IPTABLES :> ( sub { return exists($_[0]->{"SYN"}) && \\
                                  !exists($_[0]->{"ACK"}) ; } ) \\
        && !SUPPRESS_IP_$+{SRC}
.br
desc=SYN flood from host $+{SRC}
.br
action=pipe '%t: %s' /bin/mail -s 'iptables alert' root@localhost; \\
       create SUPPRESS_IP_$+{SRC} 3600
.br
window=10
.br
thresh=100
.PP
#
.br
# the content of /etc/sec/ssh-login.rules 
.br
#
.PP
type=Options
.br
procallin=no
.br
joincfset=ssh-login
.PP
type=Single
.br
ptype=Cached
.br
pattern=SSH_LOGIN
.br
context=SSH_LOGIN :> ( sub { return $_[0]->{"status"} eq "Failed" && \\
                                    $_[0]->{"srcport"} < 1024 && \\
                                    defined($_[0]->{"invuser"}); } )
.br
continue=TakeNext
.br
desc=Probe of invalid user $+{user} from privileged port of $+{srcip}
.br
action=pipe '%t: %s' /bin/mail -s 'SSH alert' root@localhost
.PP
type=SingleWithThreshold
.br
ptype=Cached
.br
pattern=SSH_LOGIN
.br
context=SSH_LOGIN :> ( sub { return $_[0]->{"status"} eq "Failed" && \\
                                    defined($_[0]->{"invuser"}); } )
.br
desc=Ten login probes for invalid users from $+{srcip} within 60s
.br
action=pipe '%t: %s' /bin/mail -s 'SSH alert' root@localhost
.br
thresh=10
.br
window=60
.PP
type=PairWithWindow
.br
ptype=Cached
.br
pattern=SSH_LOGIN
.br
context=SSH_LOGIN :> ( sub { return $_[0]->{"status"} eq "Failed"; } )
.br
desc=User $+{user} failed to log in from $+{srcip} within 60s
.br
action=cevent SSH_EVENT 0 %s
.br
ptype2=Cached
.br
pattern2=SSH_LOGIN
.br
context2=SSH_LOGIN :> \\
           ( sub { return $_[0]->{"status"} eq "Accepted"; } ) && \\
         $+{user} %+{user} $+{srcip} %+{srcip} -> \\
           ( sub { return $_[0] eq $_[1]  &&  $_[2] eq $_[3]; }  )
.br
desc2=User $+{user} logged in successfully from $+{srcip} within 60s
.br
action2=logonly
.br
window=60
.PP
#
.br
# the content of /etc/sec/ssh-events.rules 
.br
#
.PP
type=Options
.br
procallin=no
.br
joincfset=ssh-events
.PP
type=SingleWithThreshold
.br
ptype=RegExp
.br
pattern=User ([\\w-]+) failed to log in from [\\d.]+ within 60s
.br
desc=Ten login failures for user $1 within 1h
.br
action=pipe '%t: %s' /bin/mail -s 'SSH alert' root@localhost
.br
thresh=10
.br
window=3600
.SH ENVIRONMENT
If the 
.B 
SECRC 
environment variable is set, SEC expects it to contain the name of its 
resource file. Resource file lines which are empty or which begin with 
the number sign (#) are ignored (whitespace may precede #).
Each remaining line is appended to the
.B argv
array of SEC as a *single* element.
Also, the lines are appended to
.B argv
in the order they appear in the resource file.
Therefore, if the SEC command line option has a value, the option name
and the value must either be separated by the equal sign (=) or a newline.
Here is a simple resource file example:
.PP
# read events from standard input
.br
--input=-
.PP
# rules are stored in /etc/sec/test.conf
.br
--conf
.br
/etc/sec/test.conf
.PP
Note that although SEC rereads its resource file at the
reception of the
.B SIGHUP
or
.B SIGABRT
signal, adding an option that specifies a certain 
startup procedure (e.g.,
.B \-\-pid
or
.BR \-\-detach )
will not produce the desired effect at runtime. Also note that the resource
file content is *not* parsed by shell, therefore shell metacharacters are 
passed to SEC as-is.
.SH SIGNALS
.TP 
.B SIGHUP
full restart -- SEC will reinterpret its command line and resource file 
options, reopen its log and input files, close its output files and sockets
(these will be reopened on demand), reload its configuration, and 
drop *all* event correlation state (all event correlation operations
will be terminated, all contexts will be deleted, all action list variables 
will be erased, etc.). With the
.B \-\-childterm
option, SEC will also send the 
.B SIGTERM 
signal to its child processes.
.TP
.B SIGABRT
soft restart -- SEC will reinterpret its command line and resource file 
options, reopen its log file, and close its output files and sockets
(these will be reopened on demand). If the 
.B \-\-keepopen
option is specified,
previously opened input files will remain open across soft restart,
otherwise all input files will be reopened.
SEC will (re)load configuration from rule files which have been modified 
(file modification time returned by
.BR stat (2)
has changed) or created after the previous configuration load. 
SEC will also terminate event correlation operations started from rule files
that have been modified or removed after the previous configuration load.
Other operations and previously loaded configuration from unmodified rule 
files will remain intact.
Note that on some systems
.B SIGIOT
is used in place of
.BR SIGABRT .
.TP 
.B SIGUSR1
detailed information about the current state of SEC (performance and 
rule matching statistics, running event correlation operations, 
created contexts, etc.) will be written 
to the SEC dump file.
.TP 
.B SIGUSR2
SEC will reopen its log file (useful for log file rotation), and also close
its output files and sockets which will be reopened on demand.
.TP
.B SIGINT
SEC will increase its logging level by one; if the current level is 6,
the level will be set back to 1. Please note this feature is available only 
if SEC is running non-interactively (e.g., in daemon mode).
.TP
.B SIGTERM
SEC will terminate gracefully. With the
.B \-\-childterm
option, all SEC child processes will receive 
.BR SIGTERM .
.SH BUGS
With some locale settings, single quotes (') in this man page might
be displayed incorrectly. As a workaround, set the LANG environment
variable to C when reading this man page (e.g., env LANG=C man sec).
.SH AUTHOR
Risto Vaarandi (firstname d0t lastname at gmail d0t c0m)
.SH ACKNOWLEDGMENTS
The author is grateful to SEB Estonia for supporting this work.
The author also thanks the following people for supplying software patches,
documentation fixes, and suggesting new features:
Al Sorrell, Brian Mielke, David Lang, James Brown, Jon Frazier, Mark D. Nagel, 
Peter Eckel, Rick Casey, and William Gertz. 
Last but not least, the author expresses his profound gratitude to 
John P. Rouillard for many great ideas and creative discussions that have 
helped to develop SEC.
.SH "SEE ALSO"
.BR cron (8),
.BR crontab (1),
.BR execvp (3),
.BR fork (2),
.BR mail (1),
.BR perl (1),
.BR perlmod (1),
.BR perlre (1),
.BR pipe (2),
.BR sh (1),
.BR snmptrap (1),
.BR stat (2),
.BR strftime (3),
.BR syslog (3),
.BR time (2),
.BR umask (2)