Code obfuscation and controlling a processor by emulation

An individual security program (28) is randomly chosen by way of a respective key (32) and is then packaged with a games program (20) to provide an executable program file (34) which is applied to a storage media, such as an optical disc (30). Whenever the security program (28) is running, the object code it produces is obfuscated to make it difficult to overcome the protection by identifying and removing the security program. The obfuscated object code is produced by substituting a variable in source code with a function of the variable. When the source code is compiled to produce the object code, the function causes the variable to be presented in the compiled object code as a series of operations.