When people first hear about hacking, they will usually see this idea as something negative. Indeed, hacking has always been about taking advantage of unprotected or weakly-guarded sites or systems for the individuals own selfish interest. Because of this, others (often companies,) who want to strengthen the protection of their online systems turn to professionals for help. These professional hackers (sometimes known as "white hats,") use an ethical hacking methodology to help build a stronger defense against real hacking threats. By deliberately "attacking" the system, they can quickly identify its flaws, and then begin to come up with contingency plans to stall, avoid or eliminate real actual hacking attacks.
From the ethical hacking methodology, you can see that not all hacks are bad. The act of hacking ethically into a system in order to expose possible weak points, ones that real hackers, or "black hats" (due to less savoury intentions) can exploit, can help prevent the company from loss of earnings or reputation. Indeed, a lot of companies are now seeking the services of those who can perform this task because they understand that the only way to fight against skilled hackers is with another skilled hacker of their own!
Those with a strong understanding of computer systems can train to carry out these services. Though when you consider the ethical hacking methodology includes breaking into online systems, it is quite possible that many white hats today have gained their experiences originally as black hats themselves!
So long as your actions have been permitted by the company who owns the system, the mischief or disorder that you'll create during the hacking process will entirely benefit the company so long as they follow up and eliminate those weaknesses.
Ethical hackers are either hired professionals who have made a name for themselves as black hat hackers, or are real employees of the company who are knowledgeable enough to perform the task.
This is not about good or bad hackers, white hats or black hats; ultimately it is about the benefit of the company, and the protection of sensitive data they may hold. If you had a less desirable past (black hat,) but have since decided to work for the system than against it, you will be well cared for because of the service you can now provide.
