EDN magazine published today that a 15-year-old Richard Skrenta on winter break from high school wrote what is considered to be the first large-scale, self-spreading personal computer virus on January 30, 1982. The Elk Cloner virus attached itself to the Apple DOS 3.3 operating system on Apple II computer and spread by floppy disk. Elk Cloner source code (just 400 lines) is available for those who want to see it. And there is also a video of this virus.
It was originally aimed just to be a prank, but it made history. The term computer virus was first used in 1983 at a security seminar.
Fortunately the virus maker was not aiming for “create the problem, offer the solution” type business. Later virus protection became big industry.