ShieldsUP! from Steve Gibson is a great service that helps you assess your computer’s protection on the Internet. Debugging some recent router troubles, I tried turning on DMZ mode, which redirected all incoming traffic to a Mac (OS X 10.6.6) on my network. I was surprised to see the striped pattern below:

Now that’s weird. Could it be some kind of reactive firewall technique on the Mac? I don’t know, but it’s a pattern, and that certainly caught me off guard.