A method includes selecting a set of printable characters as one or more test inputs for a binary module having no known valid input. The method also includes executing the binary module with the set of printable characters as the one or more test inputs for the binary module. The method also includes determining a number of instructions executed by the binary module responsive to being executed with the set of printable characters. The method also includes generating set data including the one or more printable characters associated with the number of instructions executed for each of the one or more printable characters. The method also includes analyzing the set data to identify one or more printable characters as one or more valid inputs for the binary module based on a comparison of the number of instructions associated with the one or more printable characters and a threshold range.