CyberGlossary

Malware

Computer Virus

Also known as: Computer virus, File-infecting virus

Definition

Malicious code that inserts copies of itself into other programs or files and executes when the host is run.

A computer virus is malware that propagates by attaching its code to legitimate executables, documents, or boot sectors. Unlike a worm, it requires a user action — opening a document, running a program, or booting from infected media — to spread further. Once active, a virus may corrupt data, install additional payloads, exfiltrate information, or simply consume resources. Historically dominant in the 1990s and 2000s, viruses are now less common than worms and trojans but still appear in macro documents and infected installers. Defences include up-to-date anti-malware engines, disabling unsigned macros, application allow-listing and timely patching.

Examples

  • ILOVEYOU (2000), a VBScript virus spread through email attachments.
  • CIH/Chernobyl, which corrupted firmware and disk data on infected PCs.

Related terms