Most people think that hackers are computer criminals. They fail to recognise the fact that criminals and hackers are two totally different things. Media is responsible for this. Hackers in reality are actually good and extremely intelligent people who by using their knowledge in a constructive manner help organisations, companies, goverment, etc. to secure documents and secret information on the internet.
A white hat is the hero or good guy, especially in computing slang, where it refers to an ethical hacker or penetration tester who focuses on securing and protecting IT systems

An Ethical Hacker is an expert hired by a company to attempt to attack their network and computer system the same way a hacker would. Ethical Hackers use the same techniques and tactics as those used by illegal hackers to breach corporate security systems. The end result is the company’s ability to prevent an intrusion before it ever occurs.
The company and the Ethical Hacker enter into a legally binding contract. The contract, sometimes called a “get out of jail free card,” sets forth the parameters of the testing. It’s called the “get out of jail free card” because it’s what harbors the Ethical Hacker from prosecution. Hacking is a felony, and a serious one at that. The terms of the agreement are what transform illegal behavior into a legal and legitimate occupation.

Once the hacker has exhausted his attempts, he reports back to the company with a list of the vulnerabilities he uncovered. The list in and of itself, however, is not particularly useful. What’s most valuable is the instructions for eliminating the vulnerabilities that the Ethical Hacker provides.