1. A method to determine if a computer program in a memory of a computer is malicious, the computer program including one or more computer program instructions, each computer program instruction located at an address in the computer memory from which it can be executed, the method comprising the steps of: prior to execution of the computer program instructions, the computer identifying one or more addresses in the memory corresponding to the locations of one or more of the computer program instructions in the computer program; and during execution of the computer program instructions, the computer identifying in the computer program another computer program instruction located in another address in the memory, and in response, the computer making an indication that the computer program has an indicia of maliciousness.