Blackhat hacker

A black hat hacker (also called a cracker), is a hacker who specialize in unauthorized penetration of computer systems. They may use computers to attack systems for profit, for fun, or for political motivations or as a part of a social cause. Such penetration often involves modification and/or erasure of data, and is done without authorization.

They also may distribute computer viruses, Internet worms, and deliver spam through the use of botnets. The term may also refer to a hacker who cracks software to remove copy restriction methods: copy prevention, trial/demo version, serial number, hardware key, date checks, CD check (NO-CD) or software annoyances like nag screens and adware.