Where can I download a free firewall?

Free firewalls have become very common and represent an excellent alternative to commercial firewall packages.

Most of these firewalls run under some form of Linux, FreeBSD, or OpenBSD.

Many of these free firewalls are front-ends for the lower-level firewall packages which ship with these operating systems, such as pf (Packet Filter), ipf (IPFilter), ipfw (IPFirewall), and iptables.

Free firewall packages which you can download include: