What is a Trojan horse in cybersecurity?

Malware disguised as legitimate software — the user is tricked into installing it; it doesn't self-replicate.

Trojan = Malware disguised as legitimate software

Named after the Greek myth — appears helpful but contains hidden malicious code.

Characteristics:

• Looks like useful software
• Does NOT self-replicate (unlike viruses/worms)
• Requires user to install/execute it
• Often creates backdoors

Examples:

• Fake antivirus software
• Pirated software with hidden malware
• "Free" games or utilities

Memory tip: Just like the wooden horse in Troy — it's a gift that's actually a trap.

Go deeper:

• NIST CSRC glossary: Trojan horse — authoritative: a seemingly useful program hiding malicious code that evades security mechanisms.
• Trojan horse (computing) (Wikipedia) — explicitly notes Trojans, unlike viruses/worms, do not self-replicate.