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.
snort_inline is basically a modified version of Snort that accepts packets from iptables and IPFW via libipq(linux) or divert sockets(FreeBSD<sep/>
Firewall Builder is multi-platform firewall configuration and management tool. It consists of a GUI and set of policy compilers for various firewall platforms.