What Is iptables?
At first place the most popular firewall / NAT package running on Linux systems was ipchains. Unfortunately it had a number of limitation and the primary one of which was that it ran as a separate program, not as part of the kernel. The Netfilter organization decided to develop a new product called iptables in order to provide more flexibility. As a result of this, iptables is considered a much more faster and secure alternative. iptables has now become the default firewall package installed under most Linux distributions.

