Black hat

A black hat is a person who compromises the security of a computer system without permission from an authorized party, typically with malicious intent. The term white hat  is used for a person who is ethically opposed to the abuse of computer systems, but is frequently no less skilled. The term cracker was coined by Richard Stallman to provide an alternative to using the existing word hacker for this meaning. The somewhat similar activity of defeating copy prevention devices in software which may or may not be legal in a country's laws is actually software cracking.
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