NightMare is a scareware program distributed on the Fish Disks for the Amiga computer (Fish #448). It is generally credited to be the first scareware program of its type.
The program was developed by Patrick Evans (Nobleton, Ontario, Canada) in 1991 and was free to redistribute, with source code available from the author.[1]
When NightMare executes, it lies dormant for an extended period of time. Every five minutes, it changes the entire screen of the computer to an image of a skull while playing a horrifying shriek on the audio channels.[2]