He’s credited with inventing return-into-libc, privilege separation for Unix daemons, and I’m just quoting his Wikipedia page. He also first demonstrated heap buffer overflow exploitation. His password cracker, John the Ripper, has awesome embedded into its every fiber, from being the first cracker to use bitslice DES implementations to doing brute forcing based on statistical frequency of characters.
recognize both excellence and incompetence in the field of information security