Cybersecurity

Worm

Definition

A computer worm is a standalone malware computer program that replicates itself in order to spread to other computers. It often uses a computer network to spread itself, relying on security failings on the target computer to access it.

Why It Matters

Worms are particularly dangerous because they can spread extremely rapidly across a network without any human intervention, potentially infecting thousands of machines in a short time.

Contextual Example

The infamous "WannaCry" ransomware attack in 2017 spread using a worm-like capability. It exploited a vulnerability in Windows to automatically spread itself from one unpatched computer to another on the same network.

Common Misunderstandings

  • Unlike a virus, a worm does not need to attach itself to an existing program.
  • Worms often carry a "payload," which is the malicious code they deliver after infecting a system (e.g., ransomware or a backdoor).

Related Terms

Last Updated: December 17, 2025