A back door (also called a trap door) is a software program that allows unauthorized access to a system without going through the normal (front door) log – on procedure. Programmers who want to provide themselves with unrestricted access to a system that they are developing for users may create a log – on procedure that will accept either the user’s private password or their own secret password, thus creating a back door to the system. The purpose of the back door may be to provide easy access to perform program maintenance, or it may be to perpetrate a fraud or insert a virus into the system.