Ipfirewall

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The correct title of this article is ipfirewall. The initial letter is shown capitalized due to technical restrictions.

Not to be confused with IPFW, the initialism of Indiana University-Purdue University Fort Wayne.

ipfirewall or ipfw is a FreeBSD IP packet filter and traffic accounting facility. Its ruleset logic is similar to many other packet filters except IPFilter. ipfirewall 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. Like FreeBSD, ipfirewall is open source.

Mac OS X's ipfirewall tab in the Sharing PrefrencesPane, simply titled Firewall.

ipfirewall is composed of these components:

kernel firewall filter rule processor and its integrated packet accounting facility
logging facility
"divert" rule (NAT)
advanced special purpose facilities
the dummynet traffic shaper
"fwd rule" forward facility
the bridge facility
ipstealth