fwsnort

I recently had the chance to try out fwsnort, a software that parses the rule files that come with the Snort intrusion detection system. fwsnort then proceeds to create an equivalent iptables ruleset for as many rules as possible. The best part is that fwsnort allows users to restrict processing to any specific class of Snort rules, such as "ddos", "backdoor", or "web-attacks". This feature can even be used to restrict processing to a specific Snort rule, identified by its "snort id" or "sid".

In addition, fwsnort utilizes the iptables string match module, along with a custom patch that adds a --hex-string option to the iptables user space code. This allows for the detection of application level signatures, which is a handy tool for those trying to detect and prevent attacks.

Another useful feature is fwsnort's optional use of the IPTables::Parse module, which can translate snort rules for which matching traffic could potentially be passed through the existing iptables ruleset. Overall, I found fwsnort to be a very effective and flexible tool for building iptables rules from Snort rules. It's definitely worth giving a try!