American diplomat and lawyer Allen Dulles (1893-1969), the 5th Director of Central Intelligence and once head of the CIA listed 73 Rules of Spycraft.
“The greatest weapon a man or woman can bring to this type of work in which we are engaged is his or her hard common sense. The following notes aim at being a little common sense and applied form. Simple common sense crystallized by a certain amount of experience into a number of rules and suggestions.”
Bureau of Sabotage