A nematode is a very intriguing type of malware. To put it short, it is a virus that attempts to remove another virus, sometimes to allow their code to run on the system.
- Denzuko destroys the Brain virus, but also drops its payloads. It is known as the first nematode.
- Klez attempts to remove the CodeRed worm, but in the process drops the Elkern virus.
- The Netsky worm attempts to remove the Mydoom worm.
- Some viruses can also try to terminate processes of some viruses, like Magold.E.
- The Welchia Anti-worm initiates a payload where it removes the Blaster worm, and then installs Microsoft Updates that prevent Blaster from exploiting the vulnerability it requires to activate itself, but it slows the OS down with unnecessary instructions.