Apparently, there are still some issues with the firewall on Mac.
From Secunia:
Description:
Some weaknesses and a security issue have been reported in Apple Mac OS X, which can lead to exposure of certain services.1) The Application Firewall allows any process running as user “root” (UID 0) to receive incoming connections even though the option “Block all incoming connections” is set.
NOTE: The update changes the name of the option and updates the documentation.
2) The Application Firewall allows any process running as user “root” (UID 0) to receive incoming connections even though the executable has been added to the list of blocked applications via the “Set access for specific services and applications” option.
3) Changes to Application Firewall settings do not affect processes started by launchd until they are restarted. This may lead to exposure of certain services.
The weaknesses and the security issue have been reported in Mac OS X 10.5 (Leopard).
Solution:
Update to Mac OS X 10.5.1.
[tags]Apple OS X Firewall, Mac Firewall, OS X Firewall Weakness[/tags]