After upgrading to 10.5.1, one of the first things I did was to verify that my firewall remained enabled. So, in System Preferences/Security, Firewall tab, I verified that “Allow only essential services” was selected.
To ensure the firewall worked as designed, I then ran the “All Service Ports” test (first 1056 TCP ports) from
Shields Up.
The results indicated that no ports were open and that all other ports were in “Stealth” mode (except Port 113 (Port Authority Database) which was closed). So at first, it seemed that the firewall was indeed working as designed.
But on a whim, I reset my firewall to “Allow
all incoming connections”.
I then reran the same Shields Up test. To my surprise, the results were identical in both tests.
Thus, it seems (to me) that enabling the firewall serves no advantage.
Might it be that my router already performs/serves (duplicates?) the same functions as Apple’s firewall?
Ah, confusion in Pendragonland...