THE biggest deluge of computer viruses ever known could have been prevented, according to a Bolton IT security specialist.

George Bailey, director of Secure Systems Technology, in Deane Road, said that firms can ward off viruses by keeping on top of security software updates.

The SoBig-F virus affected one in 17 of all e-mails last week, and threatened to bring the Internet to a halt.

Networks crashed as the bug-infected computer systems were swamped with unwanted messages. Twelve million copies of the the virus were intercepted by Internet giant AOL on Thursday. The virus, which is thought to spread by taking over e-mail address books, is believed to have been created just 48 hours before it struck.

This was the latest assault on the global computer network after seven days of bombardment that has been dubbed the "worst virus week in history".

Mr Bailey said: "These viruses have caused an awful lot of problems for our partners over the last week. At the end of the day the only reason they take effect is because people don't run Windows updates.

"If people kept their critical security files updated, then 99.9 per cent of the viruses would not be effective."

The SoBig virus appears in an e-mail, which has supposedly been sent from an address found in the computer system's address book, and is marked: "Subject: Re: Your application."

Once opened, SoBig-F installs itself onto the machine, and between 7pm and 10pm every Friday and Sunday, the worm is activated to send massive amounts of spam.