Compromised systems apparently can conduct over 1,000 search engine queries a day, according to computer security firm McAfee Inc.

David Krane, a spokesman for Google Inc., said in an e-mailed statement that the company's site "experienced slowness for a short period of time early today because of the MyDoom virus, which flooded major search engines with automated searches." The company said that the virus hit "a small percentage of our users . . . at no point was the Google website significantly impaired."

Yahoo Inc., too, described the impact of the virus on its service as limited. "We're going to continue to monitor the situation," said spokesman Brian Nelson.

The original version of MyDoom attacked the Web site of a Utah technology company called SCO Group Inc., which has angered many programmers by filing lawsuits claiming it owns intellectual property related to the free, open-source operating system Linux.

While that was an attack specifically aimed to knock SCO's Web site off the Internet, some computer security workers who looked at the programming inside the latest version of MyDoom speculated that the impact on search engine Web sites may have been an accidental byproduct of MyDoom.m's programming.

"It's probably just a side effect of how its attempting to spread -- the faster it can gather e-mail addresses, the better," said Ken Dunham, director of malicious code at the Reston-based computer security firm iDefense Inc.

Craig Schmugar, the virus research manager at McAfee who named the "MyDoom" virus when it first appeared in January, agreed.

Schmugar said that the MyDoom source code has been widely available on underground Web sites since at least February and that the latest version is only different in that it uses search services to help spread itself.

MyDoom was credited by some computer security firms as being the fastest-spreading e-mail virus ever, though its sequels have generally had less impact than the first one. Schmugar said that it would not require a gifted programmer to figure out how to craft the latest modification of the bug.

"If you already had the source code, it wouldn't take a really sophisticated programmer to make the changes," he said.

There was some Internet speculation yesterday that the attack was a targeted effort at Google on the day it announced its IPO price range, computer security experts generally dismissed such speculation.

"If it were a targeted attack against Google, it was not done in an effective manner," said Oliver Friedrichs, senior manager with Symantec Corp., a Cupertino, Calif., software security firm.

Washington Post staff writer Jonathan Krim contributed to this report.