white hacker 

A white hat hacker, also rendered as ethical hacker, is, in the realm of information technology, a person who is ethically opposed to the abuse of computer systems. Realization that the Internet now represents human voices from around the world has made the defense of its integrity an important pastime for many. A white hat generally focuses on securing IT systems, whereas a black hat (the opposite) would like to break into them.

Terminology

The term white hat hacker is also often used to describe those who attempt to break into systems or networks in order to help the owners of the system by making them aware of security flaws, or to perform some other altruistic activity. Many such people are employed by computer security companies; these professionals are sometimes called sneakers. Groups of these people are often called tiger teams.

The primary difference between white and black hat hackers is that a white hat hacker claims to observe ethical principles. Like black hats, white hats are often intimately familiar with the internal details of security systems, and can delve into obscure machine code when needed to find a solution to a tricky problem. Some use the term grey hat and fewer use brown hat to describe someone's activities that cross between black and white.

In recent years the terms white hat and black hat have been applied to the Search Engine Optimization (SEO) industry. Black hat SEO tactics, also called spamdexing, attempt unfairly to redirect search results to particular target pages, whereas white hat methods are generally approved by the search engines