Quiz Entry - updated: 2026.07.14
What distinguishes a worm from a virus from a trojan?
Virus needs a host file, worm self-replicates over networks, trojan deceives the user into installing it.
* Virus vs worm vs trojan — a host file plus a user makes it a virus; self-spreading with no human is a worm; disguised software the user installs is a trojan. *
| Property | Virus | Worm | Trojan |
|---|---|---|---|
| Host file needed | Yes (attaches to exe/doc) | No (standalone) | No (IS the file) |
| Self-replicates | Yes (via infected files) | Yes (over network) | No |
| Spreads how | Shared/executed files | Exploits vulnerabilities automatically | User tricked into installing |
| Human action needed | Yes (run infected file) | No (autonomous) | Yes (install fake software) |
| Named after | Biological virus | Worm (crawls through network) | Greek Trojan Horse |
Tip: The key question is "does it need help?" — viruses and trojans need human action, worms don't.
Go deeper:
Malware (Wikipedia) — the full malware family (virus, worm, trojan, ransomware, spyware) and how each spreads.