Michelangelo Virus Hits PCs at Some Firms Early : * Technology: The disease strikes a day before its expected outbreak at companies where computer clocks were set to the wrong date.

The Michelangelo computer virus attacked a day early at more than a dozen U.S. companies Thursday, turning personal computer data into gibberish.

The disease had been expected to strike today, the 517th anniversary of the birth of the Renaissance master for whom it is named.

John McAfee, chairman of the Computer Virus Industry Assn., said it struck some companies early because their computers were set to the wrong date.

“They have come in and turned their systems on and everything’s gone,” said McAfee, whose Santa Clara, Calif.-based computer virus monitoring group has been keeping up a special watch for the disease.

McAfee was reluctant to divulge the names of companies struck by the virus.

The Oakland Tribune newspaper in Oakland, Calif., said it was hit by Michelangelo because the virus attached itself to a related virus called Stoned, which suddenly activated.

In Japan, where March 6 began 14 hours earlier than in New York, a small architectural and civil engineering firm lost an estimated $20,000 to $30,000 worth of data, including architectural drawings stored on three of its 20 PCs.

“It was a lot of work. Obviously we’re angry and furious,” said a man who asked that his company not be identified.

The Argentine national news agency DYN said Bariloche, a daily located in the southern Argentine town of the same name, also had files destroyed by Michelangelo.

Although McAfee could not estimate how many PCs were affected by the outbreak in the United States, he said he had reports from more than 12 companies.

Dataquest, a market research firm in San Jose, Calif., said a survey it conducted recently demonstrated a high rate of Michelangelo infection among PCs.

In the study, involving 600 computer sites with a total of 600,000 machines, about 15% of respondents reported finding the virus, Dataquest software analyst Peter Francis said.

“We’ve already started getting reports of activation by people whose dates are off,” McAfee said. “People don’t ordinarily monitor their computer time and date like they do their wristwatch.”

In Costa Mesa, an account supervisor at the advertising firm Salvati, Montgomery, Sakoda & Co. said he found the Michelangelo virus on one of his office computers.

Greg Smith said he found the virus along with Stoned and another called Bloody. He said the company’s software expert gave him an anti-virus program that erased the virus without damage.

Any computer compatible with the International Business Machines Corp. standard is a potential target. But the disease can be eradicated by scanning devices and special software.