Firewall

Mac OS X and Mac OS X Server include a built-in software firewall based on ipfw which is a Unix firewall. Although the firewall was included with Mac OS X 10.0 and Mac OS X 10.1, it was only configurable from the command line or using a third party utility such as Brickhouse.

Mac OS X 10.2 and later added the Personal Firewall to the sharing pane of System Preferences. Mac OS X Server can use the Server Admin utility to configure the firewall with much greater control.

When the firewall is enabled, all inbound connections are denied except for the ports that you explicitly permit.