WOBURN, Mass. -- Autumn 2006 was a stormy season. For the third month in a row there's not only a new leader in our rankings, but the entire Top Twenty is once again in a state of flux. However, worms from the Warezov family were the main troublemakers, just as they were last month.

In November, Warezov.gj, a newcomer, took first place. This worm, which was first detected on November 22nd, only took one week to become the most widespread virus in email traffic, with an impressive share of over 18%! Only a few malicious programs have shown such record propagation rates in the first month of their existence - and all of them remained at the top of the charts for significant periods of time. However, I believe this won't be the case this time. Warezov.gj will probably fall sharply in December as the worm surrenders to the onslaught of its new "siblings".

This month's surprise was the triumphal return of our old acquaintance, Nyxem.e, which immediately shot to third position in the rankings. This worm will soon be celebrating an anniversary of sorts: it's nearly a year since was first detected. And it's become one of the most widespread viruses in all of 2006.

Kaspersky Lab