A “Trojan horse” is something that appears acceptable or helpful but gains entry in order to undermine a group or system from inside. The phrase can be figurative or technical (malware); keep the intended sense clear and avoid implying secret malicious intent when the evidence only shows an ordinary unwanted consequence.
ReviewedEvidence1 sourceSectionPhrases & Idioms
Quick answer
A “Trojan horse” is something that appears acceptable or helpful but gains entry in order to undermine a group or system from inside.
Key details
Canonical Formtrojan horse
Core Meaninga person or thing that seems to join or help a group or system but is intended to deceive or cause harm from within
Further guidance
Contextual Examples
“Security software detected a Trojan horse disguised as a routine installer.”
“Critics described the amendment as a Trojan horse for a broader change; that characterization should be attributed rather than stated as fact.”
History Boundary
Current dictionary-supported meaning is published without claiming an exact inventor, coinage date, or absolute first use.
Meaning
a person or thing that seems to join or help a group or system but is intended to deceive or cause harm from within
Meaning Boundary
Do not use it as a generic label for any bad side effect. The metaphor carries an element of concealed purpose or harmful entry; in computing, it also has a specific malware sense.
Practical Use
Use “Trojan horse” when something apparently acceptable or beneficial is being described as a means of gaining entry or access so that harm, subversion, or an unwanted hidden purpose can operate from within.
Tone Boundary
The phrase is strongly accusatory when applied to people, policies, or organizations. Attribute the characterization or use more neutral wording unless hidden intent is actually established.
Usage Boundary
The phrase can be figurative or technical (malware); keep the intended sense clear and avoid implying secret malicious intent when the evidence only shows an ordinary unwanted consequence.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
“Behind closed doors” describes something done privately, secretly, or without public observation. The page distinguishes that current meaning from any unsupported story about the phrase’s exact origin.
“Black box” can refer literally to recording equipment and figuratively to an opaque system whose internal operation is not visible or understood. This guide focuses on the documented opaque-system sense without asserting unsupported origin chronology.
“Caught red-handed” means discovered in the act of doing something wrong or illegal. The expression is stronger than saying someone is merely suspected, because it centers on being found during the wrongdoing.
“Fine print” refers to small-print terms or details that may contain important conditions; Cambridge notes that “small print” is the usual UK expression. The guide stays with current documented meaning and does not add unsupported origin chronology.
“Hear It Through the Grapevine” means to learn information through an unofficial, informal chain of people. This guide publishes the current dictionary-supported idiomatic meaning and keeps exact origin, inventor, coinage, and absolute first-use claims unpublished without chronology-grade evidence.
“The inside scoop” means information that is not generally available to everyone, especially privileged or behind-the-scenes information. Merriam-Webster records “scoop” in the information sense and uses “inside scoop” in its current language examples and related editorial material.
“Keep something under wraps” means to keep it secret or concealed from public knowledge. This guide explains the established current sense without promoting an unsupported origin story.
To keep your cards close to your chest is to keep your plans or intentions secret. The metaphor is transparently connected with concealing a hand of playing cards, but exact dating is uncertain. The reviewed history source explicitly warns that popular 1860s-origin claims lack citations and treats mid-twentieth-century figurative evidence as the safer documentary floor.
