Malware authors have increased both the volume and sophistication of their attacks over the last six months. In the first half of 2005 anti-virus firm Sophos detected and protected against 7,944 new viruses - up 59 per cent from the first six months of 2004. The number of keylogging Trojans has tripled in the first six months of 2005 compared to the first half of 2004.

More computer viruses and worms mean an unprotected Windows PC (without either firewall or antivirus protection) stands a 50 per cent chance of infection by a worm after just 12 minutes online. Graham Cluley, senior technology consultant at Sophos, conceded that Windows PCs no longer ship in this unprotected state. Nonetheless the finding illustrates the need to apply basic defences (consumers can find free products aplenty if they choose to look).

The longstanding Zafi-D worm, which poses as a Christmas card greeting, made up more than a quarter of all viruses reported to Sophos so far this year. Runner up was the long-running NetSky-P worm with the bilingual Sober-N worm, which poses as offers for free tickets to the 2006 World Cup in Germany, in third place.

"The threats are consolidating - it's becoming more blurred as to whether something is a spam, a spyware, a phish or a virus problem. Businesses must ensure they are protected against all of these threats," Cluley added. ®

Viral charts 1H05 (as compiled by Sophos)

1. Zafi-D
2. NetSky-P
3. Sober-N
4. Zafi-B
5. NetSky-D
6. MyTob-BE
7. NetSky-Z
8. MyTob-AS
9. NetSky-B
10. Sober-K

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