White hat

Term used to describe a computer hacker or individual who attempts to break into a computer system or computer network or find weaknesses in computer network hardware or software. However, instead of maliciously taking advantage of these weaknesses, the individuals let the computer network administrator, company, or software or hardware manufacturer know about these issues so they can be corrected. These individuals are hired by companies and governments to probe their networks and find any vulnerabilities that may exist.

Also see: Black hat, Ethical hacking, Hacker, Security definitions