1982: Richard Skrenta, 15, writes the first PC virus code, which is 400 lines long and disguised as an Apple boot program called "Elk Cloner." Skrenta wrote the virus as a prank, aiming to trick friends who were already leery of accepting games on floppy disks from him. When a computer booted from an infected disk, a copy of the virus would be placed in the computer's memory. If an uninfected disk was then inserted into the computer, Elk Cloner would be copied to the disk, allowing it to spread from disk to disk. The prank, though annoying to victims, was relatively harmless compared with the viruses of today. All an infected computer would do was display a short taunting poem on every 50th boot.