Whether you called it Jerusalem, Friday the 13th, Datacrime, or the Columbus Day virus, the malware was first uncovered in October 1987 and the variants it inspired are remembered nearly 50 years later for the good they did. No—really, you read that correctly. Learn more in this edition of Tech Time Warp.
The Jerusalem virus attacked MS-DOS operating systems. Until Windows supplanted MS-DOS, Jerusalem, and its variants were the dominant threat to computers. The virus was a “logic bomb,” meaning it lay dormant until certain conditions were met. In this case, the virus didn’t activate itself until Friday of the 13th of any month. (Other logic bombs can trigger from a specific system event, a user action, or a combination of time, event, and action.) Once activated, a logic bomb deploys a malicious payload.
Later variants of the virus erased boot sector files, but for the early Jerusalem virus, the primary effect of the payload was to bloat infected executables until they were too large to run. That’s what Israeli university students Omri Mann and Yuval Rakavi noticed. They began working with other computer scientists to develop software that scanned machines. It rid them of the Friday the 13th virus. Mann and Rakavi distributed this software for free, but the demand was great—and the antivirus industry was born.
Contemporary media warnings about this early mainstream example of malware are fascinating. For instance, in October 1989, The New York Times called one form of malware spread—the spread of “infected diskettes”—“the computer equivalent of sharing a dirty hypodermic needle.” The Times also explained viruses could spread through infected downloads, exchanging infected files on a network, or by a bad actor.
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