The 30-year-old prank that became the first computer virus

To the author of ‪Elk Cloner‬, the first computer virus to be released outside of the lab, it’s sad that, 30 years after the self-replicating code's appearance, the industry has yet to come up with a secure operating system.
When Rich Skrenta, created Elk Cloner as a prank in February 1982, he was a 15-year-old high school student with a precocious ability in programming and an overwhelming interest in computers. The boot sector virus was written for Apple II systems, the dominant home computers of the time, and infected floppy discs.

If an Apple II booted from an infected floppy disk, Elk Cloner became resident in the computer’s memory. Uninfected discs inserted into the same computer were given a dose of the malware just as soon as a user keyed in the command catalog for a list of files.
Infected computers would display a short poem, also written by Skrenta, on every fiftieth boot from an infected disk:
Elk Cloner: The program with a personality
It will get on all your disks It will infiltrate your chips Yes it's Cloner!
It will stick to you like glue It will modify ram too Send in the Cloner!
Elk Cloner, which played other, more subtle tricks every five boots, caused no real harm but managed to spread widely. Computer viruses had been created before, but Skrenta’s prank app was the first to spread in the wild, outside the computer system or network on which it was created.

Elk Cloner took about two weeks to write in assembly language, Skrenta recalls. And if it’s mode of operation sounds simple, making it actually happen was quite a technical challenge. His earlier adventure game took longer but was more creative, like making a puzzle.
“It worked like a charm and spread all over the place,” Skrenta remembers with a chuckle. His cousins in Batimore and - years later, he discovered - a friend in the US Navy were among those whose computers caught the virus.
Not that there weren’t ways of avoiding infection.
“Elk Cloner created a rattling noise when the program started. If a disc was infected you could hear it. If you inserted an infected disc in an Apple II you can hear the head swoosh sound, an audible signature.
“It would infect a new disc if machine wasn’t rebooted. If an Apple II was rebooted every time, Elk Cloner wouldn’t have spread. But, given people computer habits, it spread like crazy,” Skrenta explained.