1. A method of enhancing command injection protection to achieve improved operation of a computer which receives input data from an untrusted source, and which operates an application program which utilizes said input data, said method comprising the steps of: creating a garbage-collected tainted value cache as a location in which the input data from the untrusted source is stored, performing a data characterization test on the input data, wherein said data characterization test comprises a data characterization test to see when said input data comprises only numerical data or only alphabetical data, storing said input data in said garbage-collected tainted value cache to create stored data when said input data did not pass the data characterization test, and not storing the passed input data in said garbage-collected tainted value cache, intercepting said stored data, when said application program invokes a method which utilizes said stored data, before said stored data is utilized by said application program, creating intercepted data and subjecting the intercepted data to a data content test, wherein said data content test comprises searching for code indicating characters, said code indicating characters being permissible characters other than alpha-numeric characters, forwarding said intercepted data to said application program for utilization when said intercepted data passes said data content test, and implementing a security action when said intercepted data fails said data content test, wherein said security action is selected from the class of security actions consisting of making a log entry, blocking execution of said application program, and shutting down said computer.