What is a Trojan Horse?

A.
A malicious program that captures your username and password

B.
Malicious code masquerading as or replacing legitimate code

C.
An unauthorized user who gains access to your user database and adds themselves as a user

D.
A server that is to be sacrificed to all hacking attempts in order to log and monitor the hacking activity

Explanation:
A Trojan Horse is an apparently useful and innocent program containing additional hidden code which allows the unauthorized collection, exploitation, falsification, or destruction of data.