2004 has become the year of the computer virus

The number of viruses being written and released continues to grow year on year, with 2004 already looking set to pass many malware milestones.

The number of new viruses detected during the first six months of 2004 is up 21 per cent on the same period last year.

The first six months of the year have been characterised by a number of big-name viruses - most notably Sasser and huge number of Netsky variants.

Sasser has accounted for more than a quarter (26.1 per cent) of all email-borne viruses. The prolific Netsky.P accounted for 21.4 per cent while the .B and .D variants accounted for 11 per cent and 6.8 per cent respectively, according to antivirus vendor Sophos, making Netsky in all its forms by far the most prolific.

Graham Cluley, senior technology consultant at Sophos, attributed the rapid spread of Sasser to the difficulty in keeping up to date with patch management.

"Sasser exploited a critical vulnerability in Microsoft's operating system in order to spread. This type of worm is proving to be extremely successful as Microsoft is finding it tough to ensure computer users apply patches as soon as the flaws are discovered."

But there is a silver lining to the cloud, said Cluley.

"Virus writers haven't had it all their own way in 2004. Increased scrutiny from law enforcement agencies and Microsoft's bounty initiative to encourage people to snitch on virus writers, led to a very high profile arrest in Germany," said Cluley referring to the arrest of Sven Jaschan, the teenage author of the Sasser worm and member of Skynet, the gang responsible for distributing Netsky, who confessed in May.