Covers using IPTABLES with the 2.4 Linux kernel. If you created the proxy server, all you have to do is add a few more IPTABLES commands to enhance the firewalling functionality of the system.
Debian is a free operating system (OS) for your computer. It uses the Linux kernel, but most of the basic OS tools come from the GNU project; hence the name GNU/Linux. It comes with over 29000 packages, precompiled software.