Patent ID: 7171693

Claim:
A method of modifying compiled code of an application program for executing on a computer to improve computer security while substantially preserving the application's original operational and functional characteristics, comprising the steps of: providing compiled code; scanning said compiled code for candidate instructions for substitution; substituting randomly generated, functionally isomorphic code in place of said candidate instructions to generate a first code polymorph, wherein the randomly generated, functionally isomorphic code is generated by random selection from a plurality of candidate codes that are substantially functionally isomorphic to the compiled code; securely executing the first code polymorph, wherein the execution comprises the steps of: generating a first CRC of at least one system file at the time of code polymorph execution initialization; generating a second CRC of said system file(s) while said code polymorph is executing; and comparing said first CRC and said second CRC to determine if code access attempts are being made.