White symbolizes goodness and purity in some cultures, while its opposite, black, stands for evil. In the United States, this symbolism was taken up in the genre of television and movies called the Western. In these shows, the costuming may often help viewers readily identify the hero and the villain by giving the former a white hat and the latter a black hat. From this association came the terms “white hat” for orthodox, respectable, and legitimate practice, or practice in the service or good and “black hat” for practices that violate norms and guidelines or that are exercised maliciously.
Being a reference to the good guys, white hat had a lot more currency for a long time. Recently, however, black hat has seen a rise in usage as it has come to refer to two types of people: one in the realm of search engine optimization (SEO); the other in the area of computer security. In the world of SEO, there are certain practices that were devised to purposely interfere with and subvert a search engine’s ability to rate articles as they were designed to. Such practices include title tag stuffing and stacking, cloaking, spamdexing, link farms, free for alls (FFAs), and link schemes—in short, any practice or technique aimed not at addressing the viewer, but at affecting the search engines’ evaluation of the page’s value and manipulating the page’s search engine ranking.
In the realm of computer security, black hat hackers or crackers penetrate computer systems and networks without authorization to do so. Although the motivation differs—black hat hackers may break into systems with the intent to inflict damage, just because they can, or on behalf of some cause, whether political or social—the end result is usually something destructive. Black hat hackers may steal data, destroy files, publish the vulnerability publicly or to other hackers without warning the system administrator. They may also unleash various computer plagues, including spam, viruses, and worms or remove copy protection.
Black hat operations are contrasted not only with white hat, but also with grey hat. Grey hat refers to a hacker who does not fall cleanly into the black hat or white hat categories. A grey hat may, for example, violate a system without permission or knowledge of the owner—a black hat practice—but either do no damage or actually patch the security breach—more in the white hat realm. Because their operations are not sanctioned, though, they don’t really fit the white hat moniker.