ipfirewall or ipfw is a FreeBSDIPpacket filter and traffic accounting facility. Its ruleset logic is similar to many other packet filters except IPFilter. ipfw is authored and maintained by FreeBSD volunteer staff members. Its syntax enables use of sophisticated filtering capabilities and thus enables professional users to satisfy advanced requirements. It can either be used as a loadable kernel module or incorporated into the kernel; use as a loadable kernel module where possible is highly recommended. ipfw is the built-in firewall of Mac OS X and DragonFly BSD. Like FreeBSD, ipfw is open source. It is used in many FreeBSD-based firewall products, including m0n0wall and FreeNAS. There is a port of ipfw and the dummynet traffic shaper is available for Linux, OpenWrt and Microsoft Windows.wipfw is a Windows port of an old (2001) version of ipfw.
Mac OS X's ipfirewall tab in the Sharing Preferences Pane (ipfw is supplemented by an application firewall in Mac OS X 10.5 and can no longer be configured through System Preferences), simply titled Firewall.
ipfirewall is composed of these components:
kernel firewall filter rule processor and its integrated packet accounting facility