FreeBSD has IPFW built in to the the OS. I wonder if that is the OS he uses.

"FreeBSD has three different firewall packages built into the base system. They are: IPFILTER (also known as IPF), IPFIREWALL (also known as IPFW), and OpenBSD's PacketFilter (also known as PF)."
http://www.freebsd.org/doc/en_US.ISO...alls-apps.html

I am running FreeBSD on one of my systems, but I only use packet filtering. I still have alot to learn about my FreeBSD system, so I can't get into alot of detail about it's firewall packages. The only reason I was able to provide any insight to this subject is because I have recently been reading the FreeBSD Handbook.