"Troj_Apost.A" is a worm rather than a Trojan horse, as its name suggests. The malicious e-mail arrives with the subject line "As per your request!" with the message, "Please find attached file for your review. I look forward to hear from you again very soon. Thank you."
When the attached file entitled "Readme.exe" is executed, it will try to copy itself to the floppy drive. It will then self-propagate by e-mailing itself to all addresses listed in the infected user's address book.
"We've had several reports of Apost over the last few days, but to be honest it's a lot smaller than Magistr or SirCam," said Graham Cluely, senior technology consultant at antivirus company Sophos. "After six months we are still getting reports of Magistr, and SirCam is even bigger, although it has not been around for as long," he added.
Apost was first captured on Monday, and since then e-mail screening company MessageLabs stopped 54 cases. Experts at antivirus company Trend Micro have categorized the worm as a medium risk, but Cluley asserted that "Apost isn't anything in particular to get worried about, despite what other vendors are saying."
Security experts warned people to update their antivirus software and to be suspicious of any unsolicited e-mail attachments.
Staff writer Wendy McAuliffe reported from London.