1. A method for generating pestware definitions comprising: receiving a pestware file; placing at least a portion of the pestware file into a processor-readable memory; following a plurality of execution paths within code of the pestware file, wherein each of the execution paths is a potential path that a processor executing the code will potentially follow; identifying particular instructions within the execution paths; storing, in a processor-readable pestware-definition file, a representation of the relative locations of each of the particular instructions within the code of the pestware file; and sending the pestware-definition file to a plurality of client devices, wherein at least one of the client devices receives a file and determines whether relative locations of each of particular instructions within code of the file received by the at least one client device match at least a predetermined percentage of relative locations of instructions in the pestware-definition file.