Abstract: The present invention is directed to a system and method for modifying a class file for the purpose of instrumentation, debugging, benchmarking, or making functional modifications to the class file. In addition, the present invention makes necessary changes to the components of the class file, so that the class file will pass the class file verifier before being executed. A class file is deconstructed into its components, and then selected components of the class file are modified by adding, deleting, or changing code within the components. The class file is then reconstructed, following all class file constraints imposed by the class file verifier. The present invention may also be used to modify selected code attributes of a network browser (i.e. a web browser) so that downloaded applets are saved to memory and modified before being executed by the information handling system.