Slammer--the first 'Warhol' worm?

One thing a friend reccomended to me was Black Ice Firewall. He said to set it to "Paranoid". When someone is even trying to sniff a port of yours, it will block the IP, and make your computer seem as though it's offline. I don't know much about firewalls, but I'm downloading the demo now to see if it really is what he says it is.