A black hat may refer to any of the following:
1. A black hat describes a deceptive user, computer hacker, or an individual who attempts to break into a computer system or computer network. Their intent is often to steal, destroy, or otherwise modify data on that computer system without permission.
2. Black hat is also a computer security conference held around the world to discuss computer security issues, events, and inform individuals of security threats that may be present on their computer networks. The first black hat was held in 1997 and consists of computer hackers, security experts, government officials, network administrators, and other computer literate individuals.
3. When referring to SEO, black hat SEO is tactics or deception that disobey's Google Webmaster Guidelines in the hope of getting more traffic to a web page. When detected Google will penalize a website causing it to either not be listed or ranked lower than other results. The opposite of a black hat SEO is a white hat SEO.