A black-hat hacker is a hacker who "violates computer security for little reason beyond maliciousness or for personal gain".
The term was coined by Richard Stallman, to contrast the maliciousness of a criminal hacker versus the spirit of playfulness and exploration of hacker culture, or the ethos of the white-hat hacker, who performs hackerly duties to identify places to repair. The black-hat and white-hat terminology originates in Western films, where heroic and antagonistic cowboys might traditionally wear a white and a black hat respectively.
Black-hat hackers form the stereotypical, illegal hacking groups often portrayed in popular culture, and are "the epitome of all that the public fears in a computer criminal". Black-hat hackers break into secure networks to destroy, modify, or steal data or to make the network unusable for those who are authorized to use the network.