iptables is built on top of netfilter, the packet alteration framework for Linux 2.4.x and 2.6.x. It is a major rewrite of its predecessor ipchains, and is used to control packet filtering, Network Address Translation (masquerading, portforwarding, transparent proxying), and special effects such as packet mangling.
You can download it from the following link: https://packetstormsecurity.com/files/download/78504/iptables-1.4.4.tar.bz2
Source: https://packetstormsecurity.com/files/78504/Linux-IPTables-Firewall-1.4.4.html