The Cascade virus (also known as Herbstlaub, "autumn leaves" in Germany) is a prominent computer virus that was a resident written in assembly language, that was widespread in the 1980s and early 1990s.

It was notable for using an encryption algorithm to avoid being detected.

In response, IBM developed its own antivirus software.

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".