Virus Top 10: Klez still clinging on

The persistent Klez worm has topped the virus top 10 for the fifth month running.

The latest statistics from Sophos Anti-Virus show that the Klez-H worm has infected thousands of computer systems worldwide over the past month despite being originally discovered last October.

The worm's H variant installs code in order to re-launch itself again, but does not destroy any files. It spreads via email attachments with varying subject lines. The worm has E and G variants, which have more deadly features such as time-activated payloads which trigger the worm on a specific day of each month.

Graham Cluley, senior technology consultant at Sophos Anti-Virus said the other virii are gaining a stronger foothold in the list. He said in a statement: "While Klez tops the virus chart again this month, more recent discoveries Frethem and Yaha are close on its heels. Yaha came to prominence as a politically motivated virus, launching a rudimentary denial of service attack on the Pakistan government's website and encouraging Indian hackers and virus writers to join forces and attack Pakistan."

1. W32/Klez-H Klez variant) 17.7 per cent
2. W32/Frethem-Fam 17.0 per cent
3. W32/Yaha-E 16.8 per cent
4. W32/Badtrans-B 5.8 per cent
5. W32/Elkern-C 3.7 per cent
6. W32/Magistr-B 2.5 per cent
7. W32/Hybris-B 1.9 per cent
8. W32/Klez-E 1.7 per cent
9. W32/Nimda-A 1.5 per cent
10. W32/Magistr-A 1.3 per cent
Others: 30.1 per cent