Virus top ten: Nimda romps to number one

Unsurprisingly, Nimda tops this month's virus top ten, with Sophos reporting that the virulent worm was responsible for almost three quarters of all calls to its virus hotline.

Other vendors calculate the impact of Nimda more conservatively, but still put it in the top spot, while Symantec recorded over 13,000 of its users hit by Nimda in the month of September.

Graham Cluley, senior technology consultant for Sophos anti-virus, said the figures showed the tremendous success of the Nimda worm.

He said: "This was an astonishing virus that really broke all the rules. The lesson to be learned here is to apply your software patches as well as your anti-virus patches. If you'd protected yourself against Microsoft IIS vulnerabilities - some of which are a year old - you'd have gone a long way to limiting this worm's damage."

Nimda, which first hit on 18 September spread in three ways - via mass-mailing, from server to server over the internet and by creating network shares within corporate IT networks.

Other viruses still impacting heavily include Sircam, Hybris and Magistr, all of which have had software and anti-virus patches available for some time.

Security managers may be given heart by the fact that recorded viruses as a whole fell in September from the previous month, the first time since May this has happened. However any sense of security may be false, as MessageLabs only detects viruses transmitted by email, thus missing out on the bulk of the traffic generated by Nimda.

The top ten viruses reported to Sophos in the month of Spetmeber are as follows:

1. W32/Nimda-A (Nimda) 71.1%
2. W32/Sircam-A (Sircam) 11.4%
3. W32/Magistr-A (Magistr) 3.6%
4. W32/Magistr-B (Magistr variant 3%
5. W32/Hybris-B (Hybris variant) 1.5%
6. W32/Apology-B (Apology variant) 0.7%
7= VBS/Kakworm (Kakworm) 0.68%
7= W32/Flcss (FunLove) 0.68%
9. W32/Bymer-A (Bymer) 0.5%
10. W32/Badtrans-A (Badtrans) 0.44%