January was the second consecutive monthtopped the virus charts, according to a report released Tuesday by the security software maker. The virus masqueraded as a Christmas greeting to trick users into thinking they were receiving an e-card from a friend.
The Zafi.D traffic made up 44 percent of reports of incidents compiled from the SophosLabs global network of research centers. An increasing trend toward shutting down offices over the holiday season may mean that the Zafi.D traffic owed much to people catching up on a backlog of e-mail when they returned to work in January.
The rest of the Sophos list featured all the big hitters from 2004, with Netsky,, and all appearing with at least one variant each. is second on the list, despite protection being available for 11 months.
"Netsky.P is still causing considerable nuisance," said Graham Cluley, a senior technology consultant at Sophos. "Protection against this worm has been available since March 2004, but unfortunately it seems there will always be computers connected to the Internet which are poorly defended, enabling the worm to continue to spread."
The full top 10 list for January 2005 looks like this:
2. - 19.4 percent
3. - 10.1 percent
4. Sober.I - 6.3 percent
5. Netsky.D - 3.2 percent
6. Netsky.Z - 3.1 percent
7. Bagle.AA - 2.1 percent
8. Netsky.B - 1.9 percent
9. MyDoom.O - 1.2 percent
10. Netsky.C - 1.1 percent
Will Sturgeon of Silicon.com reported from London.