Trojan horse

After besieging the walls of Troy for ten years, the Greeks built a huge, hollow wooden horse, secretly filled it with armed warriors, and presented it to the Trojans as a gift for the goddess Athena, and the Trojans took the horse inside the city's walls. That night, the armed Greeks swarmed out and captured and burned the city. A Trojan horse is thus anything that looks innocent but, once accepted, has power to harm or destroy—for example, a computer program that seems helpful but ends up corrupting or demolishing the computer's software.