INFECTED e-mails bearing the fastest-spreading computer virus in history have been bombarding systems in Bermuda this week.

The MyDoom virus has clogged up systems world-wide and its rapid multiplication has cost companies billions of dollars through network slow-down and lost productivity, according to experts.

Bermuda's small size and isolation has not helped the island to escape the effects of the so-called "worm".

Stephen Davidson, of local technology security specialists QuoVadis, said at times this week, more than one-third of e-mail traffic being monitored by his company had been infected.

"On Wednesday afternoon, of the thousands of e-mails we process for our clients, 36 per cent were infected," Mr. Davidson said. "By the end of the day it was down to about 30 per cent.

"The worm comes in via e-mail and, once opened, it scours your computer looking for e-mail addresses. It then tries to send messages, with a copy of the worm in it, to those addresses."

The worm e-mails come with messages designed to entice people into opening them.

"The e-mail comes in several different forms, with messages such as 'error message', 'hello', or 'hi'," Mr. Davidson said. It comes with an attached file that it asks you to open.

"Bermuda is a country where everybody knows everybody, so most of the e-mail addresses people keep are for other people in Bermuda. Therefore this type of virus has a disproportionate impact in a small country like Bermuda."

Yesterday afternoon, Mr. Davidson reported that MyDoom was still accounting for 30 percent of e-mail traffic being processed by QuoVadis.

Security experts around the world have been working around the clock to update anti-virus guards. The initial virus, MyDoom.A, appeared early this week, but MyDoom.B, a variant, is causing more security headaches.

On Wednesday, the US Government activated a "cyber alert" system to warn computer users about viruses and worms in light of the MyDoom problems. MyDoom is spreading faster than SoBig, a virus which brought down several major networks around the world last year.

And experts said yesterday that MyDoom would continue to plague e-mail users for some time as it counts down to a massive digital attack on two major software companies, SCO Group and Microsoft.

The virus is programmed to spread to hundreds of thousands of computers, from which a co-ordinated attack will be launched in a bid to knock Utah firm SCO off line on Sunday. A similar attack on Microsoft will follow next Tuesday.

Security specialists have conceded they are largely powerless to stop those attacks.