Incidents of virus-infected emails have soared to unprecedented levels this year with an estimated one in 370 messages containing malicious code.

That's the estimate from managed services firm MessageLabs which detected an email every 18 seconds during 2001.

This compares to just 184,257 viruses in 2000, which amounts to one per 700 emails.

The top five most common viruses in 2001 were SirCam.A with 537,523 copies stopped, BadTrans.B with 258,242, Magistr.A with 152,102, Goner.A with 136,585 and Hybris.B with 90,473. At the peak of its outbreak, the recent Goner worm appeared in one in every 30 emails which compares to the most infectious virus ever, the Love Bug, which appeared in an estimated one in 28 emails.

Mark Sunner, MessageLabs Chief Technical Officer, said that traditional, re-active virus scanners are no longer enough to combat this threat and proactive virus scanning using heuristics is a better approach.

Heuristics have an issue with false positives and tuning this out is much easier with live data obtained over the Internet, he added. ®