Interesting Occurrence

Okay... Here is a new one for me. Got a call from my dad saying he left his PC on last night connected to his broadband. He went to log in this morning and noticed a new ID in his user list - IWAP_WWW. He immediately deleted is and called me. I had him ensure his critical updates we all applied - they were. I had him ensure his antivirus was up to date - it was (Norton Antivirus 2004). He is running XP Home. I searched the antivirus sites and elsewhere for references. Any idea if there is a new vulnerability that has not been publicly released? Any clues? Regards, Brent