The Sasser worm dominated virus incident reports last month, according to anti-virus firm Sophos. The prolific worm accounted for over half of the support calls to Sophos in May.
Variants of the NetSky worm occupied positions two to seven in Sophos' monthly chart. NetSky also featured strongly in monthly stats from email filtering company MessageLabs. Carole Theriault, security consultant at Sophos, said Sasser affected many people because it could infect machines without user intervention. The fact it took advantage of a recently-discovered Microsoft vulnerability to spread also further its cause, she added.
Sophos analysed and protected against 959 new viruses in May. This is the highest number of new viruses discovered in a single month since December 2001, according to Sophos. By contrast rival Trend Micro reckons viral activity is on the decrease. Trend says it detected around 1,050 new strains malicious codes (computer worms, viruses, Trojans and other malware) during May, compared to 1,700 new viruses in April 2004. We've asked both companies if they can explain how they've managed to come up with diametrically opposed findings. Trend also reckons NetSky variants and not Sasser - which reached only eighth place in its charts - caused the most problems last month.
For years, anti-virus companies have failed to agree on a consistent scheme for naming viruses so it's perhaps no great surprise they can't agree on numbers either. Confused? You will be when you watch the latest episode of the anti-virus Soap opera. ®
May virus charts by Sophos