Sophos has released its top ten chart of malware threats and email hoaxes for January. Dorf malware was the worst offender, accounting for almost 50 percent of all malware seen, with Netsky coming in second place with 16.1 percent and Mytob in third with 9.8 percent.

The Dorf malware, or 'Storm Trojan’, initially spread two weeks ago, disguised as breaking news of deaths caused by European storms. A malicious attack from a new variant of the Dorf was then reported on 24 January. This time it was disguised as a romantic email that used a wide variety of subject lines in the spam campaign.

Carole Theriault, senior security consultant at Sophos, described the Dorf malware as “not a particularly sophisticated form of attack” which has proved to be a “remarkably effective method of fooling recipients into lowering their guard”.

More than 2,500 varients of the Dorf malware were seen by Sophos, which accounted for almost a third of new threats identified in January 2007. Sophos also stated that although the proportion of infected email was higher during the January period than December, it was still relatively low at 0.42 perecent.