Black Hat

A black hat is the bad character or bad guy, particularly in a western movie in which such a character would put on a black hat in contrast to the hero's white hat. The phrase is frequently used figuratively, particularly in computing jargon, where it refers to a hacker that breaks into networks or computers, or creates computer viruses.

Black Hat Hacker

Black Hat Hackers are hackers who specialize in illegal incursion. They may use computers to hit systems for earnings, for fun, or for political motivations or as a part of a social cause. Such incursion often involves modification and obliteration of data, and is done without approval and hence they should not be confused with ethical hackers.