Shoutbox

Even a closed, but present, port can expose a machine to attack. I myself use ShieldsUP! from grc.com, and given it's tested some 44 billion firewalls, I figure the info's pretty reliable. After all, whack a door hard enough for long enough, and it will eventually break.

I was going to quote the site, but I can't find the bit where that's mentioned. But anyway, only a truly stealthed system can be considered remotely close to immune from attack.