The W32/Yaha.M variant, which appeared just before Christmas, has proved contagious, infecting thousands of computers worldwide.
The virus, dubbed W32/Yaha.M by MessageLabs, has seen its numbers explode with over 7,000 copies being stopped by MessageLabs on Monday. So far, more than 17,000 copies of the virus have been detected by MessageLabs, leaping it to the fifth most common virus sent through the system since records began.
In response to the increase in occurrence, Symantec (which has dubbed the worm W32.Yaha.K@mm)has raised the threat from Category 2 to Category 3.
The worm arrives in the form of a .exe or .scr attachment to an e-mail with a variety of subjects and messages, and contains its own e-mail client to mail itself out, forging the "from" address. It also attempts to close down a number of firewalls and antivirus programs.
James Pearce reported from Sydney, Australia.