1. A computer-implemented method comprising: receiving, with a computer program stored on a computing device, input that is intended to be processed by the program; and processing said input using a redirection technique that is configured to mitigate one or more vulnerabilities which can be associated with said input, wherein said processing comprises: using the redirection technique without modifying the program's executable code, and redirecting function calls to a shield that is configured to modify said input, said redirecting comprising: receiving, with the shield, a function call, ascertaining whether any rules associated with the function call have been violated including detecting whether the function call contains a character string with excess characters, responsive to a rule being violated, modifying the input associated with the function call to provide modified input by removing the excess characters from the character string of the function call said input, and calling an original function using the modified input, wherein said processing is performed in advance of a vulnerability being present.