In a security context, a Hacker is someone involved in computer security/insecurity, specializing in the discovery of exploits in systems (for exploitation or prevention), or in obtaining or preventing unauthorized access to systems through skills, tactics and detailed knowledge. In the most common general form of this usage, "hacker" refers to a black-hat hacker (a malicious or criminal hacker); many who use the term in any other sense insist on using the term cracker to refer to such hackers. There are also ethical hackers (more commonly referred to as white hats), and those more ethically ambiguous (grey hats). The context of computer security hacking forms a subculture which is often referred to as the network hacker subculture or simply the computer underground. According to its adherents, cultural values center around the idea of creative and extraordinary computer usage. Proponents claim to be motivated by artistic and political ends, but are often unconcerned about the use of criminal means to achieve them.