Torblock is a python script that will attempt to block all known tor exit nodes from communicating with the system that it is run on using iptables firewalling rules.
The script retrieves a list of tor exit nodes from the tor project web site ( https://check.torproject.org/exit-addresses ) list. It extracts the IP addresses from the list, runs some sanity checks against them and then uses the python subprocess module to pass the IP address to iptables. Iptables is told to drop all packets from the IPs with the following command:
iptables -A INPUT -s AAA.BBB.CCC.DDD/32 -j DROP
The script was written to run on Redhat Enterprise Linux. If you run a different version of Linux you may need to make some changes to the iptables arguments in the script. You may also need to make some changes to the arguments if you run custom chains or need to log packets from the exit nodes.
The script requires the sys, re, requests, and subprocess modules. Those modules should be installed on your RHEL system if you install the base python packages with the exception of requests. If you need to install the requests module on your RHEL system, you should be able to do it with the following yum command:
yum install python-requests
This script does require root privileges since it calls the iptables command and modifies the system firewall. I believe the script is secure due to the use of the subprocess module and the sanity checking of the IP addresses retrieved from the Tor project web site. However, as with any program that is given root privileges, you should utilize extreme caution when running it.