Learn in the textbookMalware Basics and Major Infection Types
DefinitionA Trojan horse (トロイの木馬) is malware disguised as useful software so that users install it, after which it carries out unauthorized actions behind the scenes.
ExplanationIt gets in when users themselves install or run it. What it does once inside varies: destroying data, stealing personal information, or planting a backdoor (バックドア) that lets attackers in from outside.
AnalogyIt is like a gift box whose contents have been swapped: the person who receives it carries it into the house with their own hands.
Memory hookThe name comes from the Trojan War in Greek myth, where the enemy itself hauled a giant wooden horse full of hidden soldiers into the city.