Cascade

Overview
The Cascade virus was a resident computer virus written in assembler, that was widespread in the 1980s and early 1990s. It infected COM files and had the effect of making text on the screen fall down and form a heap in the bottom of the screen. It was notable for using an encryption algorithm to avoid being detected. However one could see that infected files had their size increased with 1701 or 1704 bytes. In response, IBM developed its own anti-virus software.