By Anick Jesdanun
The Associated Press

NEW YORK - A pesky computer worm snarled hundreds of thousands of machines worldwide Monday in the latest virus-like outbreak to take advantage of a known flaw with the Windows operating system.

Because the new worm, dubbed "Sasser," does not require users to click on an e-mail attachment to activate, it spreads more rapidly than most viruses. It was discovered late Friday and spread as employees returned to work and booted their machines.

The worm caused some computers to continually crash and reboot, apparently the result of bad programming by the virus writer rather than intent, security experts said. Sasser does not cause any permanent damage to files or machines, they added.

Among victims were large companies in Germany, Britain and the United States that are clients of Network Associates Inc., said Vincent Gullotto, a vice president of its anti-virus research lab. He would not name the companies.

A large television network in Europe also was hit, two security sources said, refusing to elaborate.

Delta Air Lines suffered some computer outages last weekend that affected more than 40 flights, mainly in and out of its Atlanta hub. The system was restored by Saturday night, although the incident caused delays into Sunday. Some flights at the Cincinnati/Northern Kentucky International Airport were affected.

Monday, airline spokesman John Kennedy said an investigation into the cause of the computer problems was under way "and nothing has yet been determined.''

Finland's third largest bank, Sampo, closed 120 of its offices for a few hours as a precaution Monday while technicians updated anti-virus programs.

Keynote Systems Inc., which tracks Internet performance, reported no traffic degradation, but security experts say some users could experience slowdowns if machines running Web sites or key Internet gateways are infected.

Though Microsoft Corp. announced three weeks ago the flaw that Sasser exploits - it's a Windows function called Local Security Authority Subsystem Service - many computer owners had yet to apply the software fix the company had released.

Once Sasser infects a computer, it automatically scans the Internet for other computers with the flaw and sends a copy of itself there.

David Perry, director of public education with security vendor Trend Micro, said Sasser continues a trend in which virus writers take advantage of announced flaws more and more rapidly. In the past, he said, it would take months or even years to widely exploit a vulnerability - not the weeks it took writers of Sasser.

Microsoft recommended that owners of Windows 2000 and XP computers install software patches by visiting http://windowsupdate.microsoft.com.

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Enquirer reporter James Pilcher contributed.