One of those programs popped up last week. Named "Proxy-Guzu," when executed by an unwitting user the Trojan listens on a randomly-chosen port and uses its own built-in mail client to dash off a message to a Hotmail account, putting the port number and victim's IP address in the subject line. The spammer takes it from there, routing as much e-mail as he or she likes through the captured computer, knowing that any efforts to trace the source of the spam will end at the victim's Internet address.
One early victim of the malware, posting to an anti-virus message board, says he detected it only when his desktop firewall program alerted him to large quantities of outgoing e-mail messages sent to unfamiliar addresses, with subject lines like "Don't tell your parents about this!" and "your bill."
Remember kids: TANSTAAFL. If someone offers you free pr0n just for clicking an attachment, chances are they're trying to pull a fast one. But you already knew that.