Security Onion is a Linux distro for IDS (Intrusion Detection) and
NSM (Network Security Monitoring). It's based on Xubuntu 10.04 and
contains Snort, Suricata, Sguil, Squert, Snorby, Bro, NetworkMiner,
Xplico, and many other security tools. The easy-to-use Setup wizard
allows you to build an army of distributed sensors for your enterprise
in minutes!
http://code.google.com/p/security-onion/