A black hat is a film's villain or bad guy, especially one literally wearing a black hat in a western, in contrast to the hero's white hat.

Black Hat
Black hat
Black Hat
SYSTEM, SERVER AND INFORMATION TERMINAL FOR DETECTION OF A BLACK HAT
Black-Hat/White-Hat Strategy in Bilateral Negotiation
Moving toward black hat research in information systems security: an editorial introduction to the special issue
White Coat, Black Hat: Adventures on the Dark Side of Medicine
Know your enemy: revealing the security tools, tactics, and motives of the blackhat community
Know your enemy : revealing the security tools, tactics, and motives of the blackhat community
White Coat, Black Hat: Adventures on the Dark Side of Medicine
How to manipulate curve standards:a white paper for the black hat
How to manipulate curve standards : a white paper for the black hat
One-Loop Calculations with BlackHat