Firewall Fundamentals

Chapter 7. Linux–Based Firewalls

Linux–based firewalls come in a variety of flavors. Originally, Linux-based firewalls were based on the ipfw code (which itself was taken from the Berkeley Software Distribution [BSD] of UNIX). This code comprised the original version of firewall capabilities within the Linux kernel. The next evolutionary step beyond ipfw was the ipfwadm utility (which was actually a rewrite of BSD’s ipfw utility). This firewall code and utility began to be available in Linux kernels in the 1.0 series and provided significant flexibility by allowing the administrator to do the following:

Change the default policies for all firewall ...