Reports from anti-virus specialist MessageLabs suggest that this latest attack could be worse than Sircam, currently the most damaging Internet virus.
Badtrans is a mass mailing virus that attempts to replicate using Microsoft Outlook to reply to unread e-mail messages.
Speaking on 26 November, Mark Summer, chief technology officer at MessageLabs said the company's Internet tracking service, SkyScan AV service was monitoring 100 new instances of the virus every minute.
Summer said: "On a normal day we clear about 4.5 million e-mail messages, of which 10,000 would contain viruses."On Monday [26 November] morning alone, the service has already hit the 10,000 watershed," said Summer. "At midday today we already hit 10,000 and the virus has spread to 37 countries."
This latest attack is the first MessageLabs has seen which replicates by sending replies to unread e-mail.
Summer said this was very worrying. His own e-mail basket contained more than 4,000 unread messages and in the US, people would be coming back to work after the Thanksgiving holiday to an inbox full of unread e-mail.
The virus also contains a Trojan Horse payload designed to capture user keyboard strokes.