psad is a collection of three lightweight system daemons that run on Linux machines and analyze iptables log messages to detect port scans and other suspicious traffic.
fwsnort parses the rules files included in the Snort intrusion detection system and builds an equivalent iptables ruleset for as many rules as possible.
snort_inline is basically a modified version of Snort that accepts packets from iptables and IPFW via libipq(linux) or divert sockets(FreeBSD), instead of libpcap.
snort_inline is basically a modified version of Snort that accepts packets from iptables and IPFW via libipq(linux) or divert sockets(FreeBSD), instead of libpcap.
This page serves as an online resource for the book Linux Firewalls: Attack Detection and Response with iptables, psad, and fwsnort written by Michael Rash and published by No Starch Press in September, 2007.