There are 16 variants.
When the virus is in memory, it hooks INT 21h to infect any executable that is run or accessed by DIR or COPY command.
After the machine has been infected for two months, the virus activates by showing a green caterpillar crawling across the screen, eating the text as it goes and spitting it back out in a different color. The user cannot stop it until reaching the bottom of the screen.
This family has 16 variants in total:
- Virus.DOS.Caterpillar.1783 (A and B)
- List of variants of the Caterpillar virus on VX Heaven