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April 26, 1999
Web posted at: 10:46 p.m. EDT (0246 GMT)

NEW YORK (CNN) -- The computer bug known as Chernobyl appears to have affected far fewer PCs than the recent Melissa virus, although its bite has proved far more deadly for its unfortunate victims.

"I've talked to people who, literally, were crying on the telephone -- a woman whose poetry book was almost done and was completely lost, a man whose doctoral dissertation was lost," said Mikko Hermanni Hypponen, of the computer security firm Data Fellows Ltd. in Finland.

The firm reported the heaviest damage in Asia and some parts of Europe on Monday, the 13th anniversary of the Chernobyl nuclear disaster.

The Chernobyl virus was known to infect only a few dozen PCs in the United States, the Computer Emergency Response Team (CERT) at Carnegie Mellon University in Pittsburgh reported.

The virus is a variation of the "CIH" virus, designed to strike on the 26th of each month. It's believed to have originated in Taiwan.

CIH is also known as a "space filler virus," because it secretly fills file space on computers and thwarts antivirus software already in place.

It was programmed to infect computers using Windows 95 and Windows 98.

Unlike Melissa, which spread through e-mail but did no direct damage, the Chernobyl virus required a person to launch an infected program that then contaminated the computer.

The virus attempts to erase a computer's hard drive and muddle the computer's system settings, or BIOS, preventing the machine from restarting.

"Unlike Melissa, this is causing real problems and serious loss of data for some people," Hypponen said. He estimated that repairs could run into the millions of dollars.

Its unclear whether warranties from PC makers will cover any of the problems. CERT officials said that data recovery service may be able to salvage lost data.

It has posted information on vendors and answers to commonly asked questions at

The Associated Press and Reuters contributed to this report.