logwatch is a packet filter / firewall / IDS log analyzer written by Boris Wesslowski originally for RUS-CERT. It supports a lot of log formats and has many analysis options. It also features incident report and realtime response capabilities, an interactive web interface and internationalization. fwlogwatch is open source software under the GPL
FieryFilter is an interactive desktop firewall for Linux. It will ask the user every time a new network connection is made if they want to allow or deny it. The user is able to generate rules from connections and thus minimize the amount of questions asked.
SmoothWall Express is an open source firewall distribution based on the GNU/Linux operating system.
SmoothWall is configured via a web-based GUI, and requires absolutely no knowledge of Linux to install or use.