The Cascade virus was a prominent computer virus that .com files and made the effect of text on the screen fall down to the bottom.
Coming with a number of variants, the Cascade virus first checks the BIOS for the string. After it finds what it needs, the virus became memory resident so when a .com file is run, the virus infects it. Cascade infects the file by replacing the first 3 bytes by the file with its own. The virus will then execute the infected file when it's accessed between October 1st and December 31st of 1988, making characters on the screen fall randomly. It may also cause the infected machine to emit some noises.
The virus used an encryption algorithm to prevent itself from being detected. However, users could discover the the virus at its dormant state from the increased file size.
The virus has infected nearly an entire IBM office in Belgium. IBM was prompted to quickly release an antivirus for it.
