The most popular modification of the Suriv family of resident file viruses was a virus called Jerusalem by an unknown Israeli programmer, which caused the global viral epidemic and the first real pandemic. It was this virus that started the first computer pandemics, which are viral epidemics spread across different countries.

The  virus Jerusalem performed several harmful functions. The most detrimental was the destruction of all programs downloaded to the computer on Friday the 13th. As Friday’s coincidence between the 13 days of the week is rare, most of the time, the virus spread unnoticed without any interference from users. Meanwhile, 30 minutes after downloading into the computer memory, the virus slowed down the XT computers by 5 times, as well as it displayed a small rectangle in the text window of the screen.