Sober December for viruses

The Sober C worm topped the infection charts for December, with a late burst of activity after its release on 21 December.

Despite this, the many MiMail variants dominate the top 10 viruses for last month, according to figures released by security software firm Sophos.

There are now 12 MiMail variants in the wild with K, J and C spreading the furthest.

Carole Theriault, security consultant at Sophos, said in a statement: "Despite Sober-C's top position in the chart, the different Mimail variants accounted for nearly a third of all reports at 29.7 per cent.

"With more than 700 new viruses arriving in our lab during December, it's fair to say that virus writers were not interested in taking a break over the festive period."

Many MiMail variants are specifically designed to gather confidential information that could be used for identity theft.

This ranges from simple email harvesters, to 'phishing' attacks that seek users' PayPal or bank details. The worm is thought to have originated in eastern Europe.

The Sober C worm uses bilingual English/German headers and the payload can be a exe, scr, pif, com, cmd or bat file.

The worm copies itself to the Windows system folder as syshostx.exe and two other randomly selected filenames, and copies itself into the shared folder of popular peer-to-peer client Kazaa.

The Sophos top 10 viruses and hoaxes for December can be seen here.