Definitions of trojan:

• noun:   a program that appears desirable but actually contains something harmful

  Example: "The contents of a trojan can be a virus or a worm"

• noun:   a native of ancient Troy
• adjective:   of or relating to the ancient city of Troy or its inhabitants

  Example: "Trojan cities"

• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #17106)