A person who used his or her expertise to gain access to other people's
computers to get information illegally or do damage is a
A person who used his or her expertise to gain access to other people's computers to get information illegally or do damage is a hacker.
While this term originally referred to a clever or expert programmer, it is now more commonly used to refer to someone who can gain unauthorized access to other computers. A hacker can "hack" his or her way through the security levels of a computer system or network.
Hacking.In computer science, hack verb means gain unauthorized access to computer data: to use a computer or other technological device or system in order to gain unauthorized access to data held by another person or organization; a transitive verb meaning cope with something: to succeed at or endure something.