Last month's Bugbear-B worm was the most pernicious virus
in the first half of 2003. Security firm Sophos received reports
about 3,855 new viruses, a 17.5% increase compared to the same
period last year, the firm said.
Bugbear-B, which morphs its contents and can turn off some
firewalls and anti-virus software, accounted for 12% of the reports
the company received.
Graham Cluley, senior technology consultant at Sophos, said all 10
viruses were executable Windows 32 viruses spread via e-mail.
"Companies can protect themselves by blocking executable code at
the e-mail gateway. These viruses should not have had anything like
the impact they did," he said.
Eight of the viruses can spread using more than one method such as
e-mail, internet relay chat and network sharing - a trend Sophos
expects to continue.
The remaining four places in the top five were taken by Klez-H, and
variants of the Sobig virus, including Sobig-C, which posed as a
support e-mail from Microsoft's Bill Gates. The impact of Sobig
makes it the biggest virus threat encountered this year so far.