1. So-called "ethical" hackers who work with clients in order to help them secure their systems. White-hats can be: members of tiger teams system hardening specialists researchers looking for vulnerabilities (with the goal of finding them and removing them before the black-hats). Contrast: Whereas a "white-hate" is considered a "good guy", a "black-hat" describes the "bad" hackers. See also: penetration testing From Hacking-Lexicon