The family of Mimail worms, geared to carry out ''phishing'' scams, littered the list of the worst viruses for last month. Anti-virus vendors report that the worms accounted for more than a quarter of all virus reports in November.
''It is pretty unusual to have so many variants of the same worm in the top 10,'' says Graham Cluley, senior technology consultant for Sophos, Inc., an anti-virus software company based in Lynnfield, Mass. ''The author has been pretty successful in spreading the worm and having a big impact.''
Cluley says analysts believe the author of the Mimail worm has connections in the spam world, since Mimail-L attacks anti-spam Web sites and goes so far as to suggest that anti-spammers are involved in child pornography. ''They're trying to make anti-spammers ineffective and put them out of business,'' adds Cluley. ''The worm has been fairly successful at spreading, but hasn't had a dramatic impact on those Web sites. The anti-spammers have put measures in place to avoid the denial-of-service attacks, and so far the anti-spammers are winning the war.''
Most of the Mimail variants, however, are built to line the author's pockets.
Steve Sundermeier, vice president of products and services at Central Command Inc., an anti-virus company based in Medina, Ohio., explains that the worms are written to stealing credit card information and social security numbers.
''It's not a new technique but it's an increasing fad -- writing computer viruses to increase financial gain rather than just boost an ego,'' adds Sundermeier. ''It's something we need to keep an eye on.''
While Mimail littered the virus scene last month, the top ranked virus, according to at least one anti-virus company, actually was the Sober-A worm.
Sober might have skimmed over the United States, but it hit hard in Europe, especially in Germany. Written largely in German, the worm contained special miming coding that allows it to initially evade detection. Anti-virus companies had to update scanning engines to detect this miming type, and it quickly spread in the mean time.
''Sober-A cunningly disguises itself using a multitude of subject titles and messages, making it difficult to spot,'' says Chris Belthoff, a senior security analyst at Sophos. ''It can even present itself in German if it thinks it is being examined on a German user's computer.''
Sophos' list of top 10 viruses, in order of first to tenth, is Sober-A, Mimail-C, Mimail-F, Dumaru-A, Mimail-A, Gibe-F, Nachi-A, Mimail-J, Klez-H, and Mimail-E.
Central Command's list, similarly, is Gibe-C, Sober, Klez-E, Mimail-G, MimailC, Hawawi-G, Mimail-I, Mimail-J, Mimail-H, and Bugbear-B.