Hacker
Person breaking into system and software security
Traditionally, the term 'hacker' applied to anyone tinkering with the internals of computer systems and software. Nowadays, it is generally used to refer to those attempting to breach computer security, either for research, finding and fixing vulnerabilities, or for malicious or fraudulent purposes.
The term is also used by several long-running communities, and many legitimate hackers object to the term being used to indicate criminality, preferring to retain the separation between the terms 'hacker' and 'cracker'.