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and, when its counter reached four, it trashed the diskette. This was achieved by overwriting the diskette with ‘garbage’ collected from another part of the computer.

The university’s senior computer consultant, Ken van Wyk, realized he had a problem when students began complaining that their diskettes didn’t work. At first there was a trickle of bad diskettes, then a flood. Something was zeroing out the diskettes, and van Wyk guessed that it was probably a virus.

Van Wyk worked for five days to isolate the bug and find a cure. He discovered that, unlike Brain, the Lehigh virus did not infect the boot sector; instead, it hid itself inside one of the three start-up programs that are triggered after the boot had performed its function. Like Brain, the virus jumped into memory whenever a computer was started up from an infected diskette. Van Wyk also discovered that the antidote was simplicity itself: all he needed to do was delete the infected start-up program and replace it with a clean one. The data on the trashed diskettes, however, was unrecoverable. Van Wyk later advised colleagues at other colleges that the virus ‘is not a joke. A large percentage of our disks have been gonged by this virus in the last couple of days.’

Later that year the university suffered another attack from a modified version of the same virus. This one trashed a diskette after infecting ten files, as opposed to four. The longer delay made the new version of what was by then known as the Lehigh virus more insidious, in that it infected more diskettes with versions of itself – and hence propagated more widely – before unleashing its payload. But because the antidote was by then known to van Wyk, the clean-up operation was quick.

The writer of Lehigh was never discovered, though he was assumed to be a student at the university.

Curiously, the professor of electrical engineering and computer science at Lehigh when the viruses attacked was Fred Cohen, by then Dr Cohen. It was Cohen who had, two years previously, written the dissertation that had first coined the expression ‘computer virus’ – and helped stir so much interest in what had previously been known as self-replicating programs. Cohen’s presence at the university may have piqued the interest of the student virus writer.

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