SAN FRANCISCO, July 26: A fast-spreading computer worm that uses Web search sites to find victims made a broad assault on computers worldwide on Monday, causing problems for Google Inc. on the day it offered new details about its initial public offering, security experts said.

The spread of the worm, a variant of an Internet attack called MyDoom, was blamed for sporadic outages and slowdowns on Google - the most popular search engine - as well as the search sites of Yahoo and AltaVista.

The new MyDoom worm searches victims' computers as well as Internet search engines for e-mail addresses, and propagates itself by sending an infected file to the addresses it finds, security researchers said.

"Those search requests have been overloading the search engines," said Lloyd Taylor, vice president of technology for Keynote Systems Inc, which measures Web site performance. The worm, Taylor said, was believed to be slowing performance on Google, AltaVista, a business of Overture Services Inc, and the Web site of Yahoo Inc.

A Yahoo spokesman said the effect of the slowdown was limited solely to their search engine, and said the site was no longer feeling its effects. Computer security software vendors sent warnings to customers about the worm, which has been called MyDoom.m or MyDoom.o. The original MyDoom worm spread to hundreds of thousands of computers earlier this year.

Symantec Corp, a maker of computer security software, said it had received 250 reports about the new worm in two hours, on pace with the original MyDoom attack in January. "This is certainly equivalent to what we saw back then," said Oliver Friedrichs, a senior manager with Symantec's security response group. -Reuters