A Trojan horse is malware that presents itself as useful or legitimate software to trick a user into opening it.

### Why this is right The statement describes the Trojan's defining deception: it appears useful or legitimate, encouraging the user to open it. Its disguise is different from a worm's self-propagation or a rootkit's concealment. ### The concept A Trojan horse depends on deception rather than a particular replication method. Once opened, it may deliver other malware or perform another harmful function. Malware can combine roles, so a Trojan may also install a backdoor. ### Terms - **Trojan horse**: Malware disguised as useful or legitimate software. - **Backdoor**: A mechanism that allows an attacker to control or access an affected system. ### Remember A Trojan tricks the user into opening it; the disguise does not make the software safe.