1. A non-transitory computer readable medium storing instructions for replacement of a system function in an application with a customized function, that when executed by at least one processor cause the at least one processor to: shift at least one existing load command in a file of the application to accommodate at least one additional load command; and add the at least one additional load command to the file, wherein the at least one additional load command identifies additional instructions that when executed cause the at least one processor to change at least one pointer of the application from a first value that points to the system function to second value that points to the customized function.