Local computer users appear to have escaped variants of a Windows worm which spread quickly across the US hitting computers at ABC, CNN, The Associate Press, The New York Times and Caterpillar Inc., just a week after Microsoft Corp. warned of the security flaw.

While ABC News producers had to use electric typewriters on Tuesday to prepare copy for their ?World News Tonight? broadcast, according to spokesman Jeffrey Schneider, two ISPs ? Logic and North Rock ? which spoke with yesterday afternoon reported no outbreaks with local clients.

Beyond the fact that the ISPs have filtering systems that would generally weed out such attachments, Ch? Barker, marketing co-ordinator at North Rock Communications.

Stephen Davidson said the QuoVadis sweeper service had seen the worm sporadically, but it was not impacting customers. Since all viruses require a certain amount of human interaction to propagate, he said that was difficult to predict how they will spread internationally and the speed with which they will do it.?

Reports of problems were however also isolated in Europe and Asia, and it appeared the worst damage was happening on US computers, but newspaper columnist Bob Mellor said that since viruses evolve there could be hundreds in a few days. He adds that viruses usually hit the US and only hit Bermuda four to five days later.

Anti-virus research firm F-Secure reported four new variants of the bug emerging yesterday, bringing the total to eleven. Mikko Hypponen, the company?s manager of anti-virus research said the variations apparently had been programmed to compete with each other ? one worm will remove another from an infected computer.

Most anti-virus companies rated the threat as low to moderate yesterday morning. McAfee Inc. considered one variant of the worm a high risk, but it categorised other versions as low risk.

Dave Cole, director of security response for Symantec Corp., said the threat appeared to have stabilised despite the appearance of new variants. He said most companies, by now, have applied the necessary software fixes to address the underlying vulnerability.

?The vast majority of the big infections have taken place,? he said.

The worms caused the most problems at companies with large, networked computer systems, rather than among individual computer users, David Perry, a security analyst at Trend Micro Inc., a computer security company, said on Tuesday. The worms can attack a system without needing to open any software, so some users would be infected without knowing it.

Microsoft Corp. released a ?critical? patch August 9 for the vulnerability, which is most severe on Windows 2000 systems. Those computers can be accessed remotely through the operating system?s ?Plug and Play? hardware detection feature. Protective patches, plus instructions for fixing infected systems, are posted on Microsoft?s website.

As experts predicted, the Windows hole proved a tempting target for rogue programmers, who quickly developed more effective variants on a worm that surfaced over the weekend and by Tuesday had snarled computers owned by companies that were slow to bolster their systems

David Maynor, a security researcher with Atlanta-based Internet Security Systems Inc.said some IT professionals who considered their networks safe because they run Windows XP or 2003 were mistaken. The worms are automated Internet ?bots? that need find only one unprotected computer running Windows 2000 within a network to propagate in the system.

The worm copies itself and then searches networks for other unprotected machines, causing no damage to data but clogging networks and rebooting its host computer.

?We did not see a widespread or fast spread of this in the first 24 hours,? said Debby Fry Wilson, director of Microsoft?s Security Response Center. ?Over the last 24 hours, we?ve see variance, where other hackers will take the work and try to unleash a variant of the worm. So the worm continues to take on different forms.?

Mr. Mellor, who is also the technical sales manager for Bermuda Microsystems Group, said the only way for local computers to really protect themselves is to get virus protection, anti-spyware and anti-adware. A personal firewall may also be a good idea.

He adds that it is also important to make sure virus protection is up to date and said that leaving the live updates switched to automatic will allow updates every time the computer is switched on. Mr. Mellor also recommends scanning the computer on a weekly basis and being consistently weary of attachments, even from people you know. Users should be particularly careful about attachments with dot doc (.doc) or dot exe (.exe) attachments.