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SESK: Stuff Everyone Should Know · sesk.info/secplus-trojan-horse

Which malware looks like a useful program but has a hidden malicious purpose and does not replicate?

Trojan horse, it appears benign but hides a malicious purpose.

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  1. A Trojan horse ✔
  2. A worm
  3. A virus

Why: Like the ancient story, it gets in by looking harmless. Unlike viruses and worms, a Trojan does not replicate; the victim installs it.

Huh, didn't know that: NIST says Trojan horses either replace existing files with malicious versions or add new malicious files to hosts.

The dad joke
The Trojan said, I come bearing gifts. The firewall said, I will take that in the sandbox.
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References

Answer: A Trojan horse. Like the ancient story, it gets in by looking harmless. Unlike viruses and worms, a Trojan does not replicate; the victim installs it.

  1. NIST SP 800-83 Rev. 1, Guide to Malware Incident Prevention and Handling nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-83r1.pdf
    A Trojan horse is a self-contained, nonreplicating program that, while appearing to be benign, actually has a hidden malicious purpose.
    Checked 2026-10-10.

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Security & PrivacyWhich malware spreads by inserting copies of itself into host programs or data files?Security & PrivacyWhich malware is self-contained and spreads across a network on its own, without user action?Security & PrivacyMalware that hides its own presence by modifying operating system functions is called what?

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