What is a computer worm?

Worms are malicious programs similar to viruses: they cause havoc on devices and are able to self-replicate.

What they are after

Unlike viruses, which need human action to propagate, worms are able to send out hundreds of thousands of copies of themselves via email, or spread via USB devices and shared folders.

Known cases

Some of the most high-profile cases of worms include:

  • ILOVEYOU, which spread via email and caused businesses over 5.5 billion dollars in damage
  • Stuxnet, which attacked Iranian nuclear centrifuges, and was spread via USB devices
  • SQL Slammer, which slowed down the Internet for a brief period of time by attacking Internet hosts
  • Blaster worm, which forced computers to repeatedly and automatically reboot

How to block worms

Avira Free Antivirus protects its users from worms.