Hackers break into systems for non-malicious reasons such as to test system security vulnerabilities. black-hat gray-hat white-hat green-hat

These are white-hat hackers. They are typically hired by the company doing the testing as a way of making sure that there are no bugs or holes in the code or program that could be exploited. The ethical hacker would look for ways to get around these issues and helps the company strengthen their programs or sites.