mrsteveman1 (1010381) writes "Heise Security gives the recently released OS X 10.5 "Leopard" firewall a very poor review, going so far as to compare it to Windows XP before Service Pack 2. In testing they have found numerous ports to be open but unreported in the GUI.
"The Mac OS X Leopard firewall failed every test. It is not activated by default and, even when activated, it does not behave as expected. Network connections to non-authorized services can still be established and even under the most restrictive setting, "Block all incoming connections," it allows access to system services from the internet.""