Like many other people, yesterday I found my inbox full of messages saying the address I'd email was bad. My problem wasn't bad addresses. It was that I hadn't sent the messages in the first place.
I emailed panix's support to express concern, lest I be dumped as a spammer. They reassured me that it was most likely someone else's virus problem. A virus on someone else's computer had snagged my email address from their address book and inserted me as a return address.
This evening, I find that the problem was written up by the Associated Press:
The e-mail message that carries Sobig.F has the subject line "Re: Details" and the message "Please see attached file for details." If a recipient clicks on the attachment, which can have multiple names ending in the .pif file extension, the computer will be infected.
The virus will then send itself out to names found in the victim's address book and will use one of these names to forge a return address. As such, the infected party may not quickly learn of the infection, while an innocent party may get the blame for helping to propagate it.