Macintosh Genuine Advantage™
See “Mac OS X Server Firewall Serial Hole:”
…What they haven’t noticed yet is Mac OS X Server 10.4 overrides an explicit administrator firewall security setting to keep its copy protection functional.
OSXS 10.4’s “Server Admin” lists “Serial Number Support” on UDP port 626 under its firewall pane, with an option to turn it off. You can, in fact, block that port with the UI. And it will work for a little while.
However, serialnumberd will eventually notice this and re-enable UDP port 626 itself. This results in a disparity where Server Admin’s UI says you have port 626 disabled, but it’s clearly active in the “Active Rules” pane.
I promised not to comment. I think it’s still fair to link.