A turn-key Linux security distribution based on IPCop and Red Hat
fwknop implements an authorization scheme that requires only a single encrypted packet to communicate various pieces of info.
A Linux firewall distro
a linux based firewall distribution with a lot of extras
A Linux-based router and firewall offering a free community edition and two commercial editions with support.
fwdaemon is a Linux networking firewall runtime backend.
ips-qos software is a flexible firewall and traffic shaping tool.
The SINUS Firewall is a TCP/IP packet filter for Linux.