The Cascade virus (also known as ''Herbstlaub'' in Germany) is a prominent
computer virus
A computer virus is a type of computer program that, when executed, replicates itself by modifying other computer programs and inserting its own code. If this replication succeeds, the affected areas are then said to be "infected" with a compu ...
that was a resident written in
assembly language
In computer programming, assembly language (or assembler language, or symbolic machine code), often referred to simply as Assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence be ...
, that was widespread in the 1980s and early 1990s. It infected .
COM file
A COM file is a type of simple executable file. On the Digital Equipment Corporation (DEC) VAX operating systems of the 1970s, .COM was used as a filename extension for text files containing commands to be issued to the operating system (simi ...
s and had the effect of making text on the screen fall (or cascade) down and form a heap at the bottom of the screen. It was notable for using an
encryption
In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decip ...
algorithm to avoid being detected. However, one could see that infected files had their size increased by 1701 or 1704 bytes. In response,
IBM developed its own
antivirus software
Antivirus software (abbreviated to AV software), also known as anti-malware, is a computer program used to prevent, detect, and remove malware.
Antivirus software was originally developed to detect and remove computer viruses, hence the nam ...
.
The virus has a number of variants. Cascade-17Y4, which is reported to have originated in Yugoslavia, is almost identical to the most common 1704 byte variant. One byte has been changed, probably due to a random "mutation". This, however, has resulted in a "bug" in the virus. Another mutated variant is also known - it infects the same file over and over.
References
F-Secure Computer Virus Information Pages: Cascade
External links
Video of the Cascade virus in action(YouTube)
{{Hacking in the 1980s
DOS file viruses
Hacking in the 1980s