IPFilter or commonly referred as ipf is a software package that can be used to provide network address translation (NAT) or firewall services. It can either be used as a loadable kernel module or incorporated into the UNIX kernel; use as a loadable kernel module where possible is highly recommended. Scripts are provided to install and patch system files, as required. Author and maintainer is Darren Reed.
IPFilter comes as a part of FreeBSD, NetBSD and xMach. Operating systems that IPFilter is known to work with are listed below.