CyberGlossary

Malware

Trojan Horse

Also known as: Trojan, Malicious trojan

Definition

Malware that disguises itself as a legitimate program to trick users into running it, delivering a hidden malicious payload.

A trojan horse (or simply trojan) is malware that hides inside something the user wants — a cracked game, a fake invoice, a phony software update, a pirated installer. Unlike viruses and worms, trojans do not self-replicate; they rely on social engineering and user execution. Once running, they can install backdoors, steal credentials, log keystrokes, drop ransomware, or recruit the host into a botnet. Many modern malware families (banking trojans, RATs) follow this pattern. Defences combine email filtering, code signing, application allow-listing, EDR, user awareness, and least-privilege execution policies.

Examples

  • Emotet, originally a banking trojan that became a major malware distribution platform.
  • Zeus/Zbot, a banking trojan that stole online-banking credentials for years.

Related terms