Got a call from a friend of mine. He was complaining that he must have a Trojan horse on his computer since his ISP told him he had downloaded more than 4 GB of data (he only has a 500MB/month rate).
After checking his computer for some time and didn't find anything, I suddenly heard a sound I knew: It was Castle Crashers on XBOX.
So I got to the room of his boy, saw a XBOX 360 and opened the downloads:
So much for my "You must have a unknown virus" theory...