A hacker is most commonly a person who seeks unauthorized access to a computer system or network. The word is also used for a skilled programmer or computer enthusiast. In computer security, it may describe an intruder or an authorized specialist who tests systems and reports vulnerabilities. Programmer and free software communities apply the term to people who explore programmable systems, modify software, or find ways around technical limits. Its meaning depends on context, and communities disagree over who may claim it.
The computing use of the term developed in student culture at the Massachusetts Institute of Technology during the late 1950s and early 1960s. At MIT, hacking ranged from playful technical work and pranks to unauthorized interference. During the 1970s and 1980s, personal computers and modem-connected networks took hacker culture beyond academic laboratories. Publicized intrusions and arrests, the 1983 film WarGames, and computer-crime laws shifted public usage toward unauthorized access. Security consulting, conferences, coordinated vulnerability disclosure, and bug bounty programs later gave some hackers recognized professional roles.
Hacker communities include programmer and free-software hackers, hardware hackers, phreakers, members of the computer underground, security hackers, and hacktivists. Their aims and legal status vary. Many value technical skill, experimentation, information sharing, and recognition from peers. Communities form around software projects, online forums, informal groups, hackerspaces, and conferences. Access may depend on skill, trust, and familiarity with group norms; even formally open communities can have cultural barriers. In security work, authorization and agreed limits separate professional testing from access without permission. Copyright law and software licenses set conditions for studying, modifying, and distributing programs; some laws also restrict the circumvention of technical protections.
News and popular culture portray hackers variously as criminals, cyberterrorists, socially isolated technical prodigies, activists, defenders, and security professionals. The favorable use of hack for an inventive solution has spread beyond computing in terms such as hackathon, civic hacking, biohacking, growth hacking, and life hack.
Terminology and scope
Within computing, communities disagree over which uses of hacker are legitimate and who may claim the label.
Etymology and early uses The verb hack, from Old English, originally meant to cut or sever with repeated blows, and hacker was used for a person who hacked in that physical sense centuries before electronic computers. The computing use developed from student slang at the Massachusetts Institute of Technology (MIT). The first edition of the Tech Model Railroad Club's dictionary, compiled in 1959, described a hack as an undertaking without a constructive purpose and a hacker as its practitioner. Before its close association with computers, the label involved playful tinkering and pranks involving machinery.
A negative usage also appeared early. In 1963, MIT's student newspaper, The Tech, called students who disrupted telephone services and made unauthorized long-distance calls "telephone hackers". Legal scholar Fred R. Shapiro documents both non-malicious tinkering and unauthorized interference in MIT usage before the word entered wider public use.
Competing definitions Current dictionaries give two principal computing senses of hacker, an expert in programming and computer problem-solving and, more commonly, someone who attempts or gains unauthorized access to computer systems. Programmer and free software communities often use the word positively for people who enjoy exploring programmable systems, modifying software, and finding clever ways around technical limits. In computer security, the term includes lawful penetration testers and security experts as well as people who act without permission.
Vulnerabilities may be discovered and reported by researchers, developers, system administrators, users, academics, security companies, or government organizations. Not all of them use security researcher or hacker as a self-description. The senses of hacker overlap in skill and method but differ in authorization, purpose, and community identity. Outside computer security, hacker may describe an expert or enthusiast in another field or someone who works around practical limitations.
Related terminology Programmer and free-software communities sometimes reserve hacker for a technical enthusiast and use cracker for someone who breaks into systems for malicious or illegal purposes. The distinction emerged during the 1980s in response to negative media portrayals. It remains disputed because lawful and unlawful hacking may use the same techniques. General dictionaries continue to list unauthorized computer access as a standard meaning of hacker.
An ethical hacker or white-hat hacker is a security professional who tests systems lawfully. A black hat acts illicitly or without sanction. A gray hat may act without permission but without the malicious intent usually associated with black hats.
A cybercriminal commits crimes through computers or the Internet. A script kiddie is an informal, disparaging term for a low-skill intruder who relies on programs written by others. A phreaker is someone who gains illegal access to or manipulates telephone systems. A hacktivist is someone who uses hacking to pursue political, social, religious, or ideological goals.
Historical development Early technical culture Members of the Tech Model Railroad Club learned about switching circuits and logical control through the relay systems used to run their model railway, and some later experimented with computers made available to students at MIT. A computer-hacker community formed around MIT's TX-0 from about 1958 and expanded after a PDP-1 was installed in 1962. Unlike most computers of the period, which were operated by specialist staff, these machines could be used directly by members of the MIT community. The community had links to Project MAC and the MIT Artificial Intelligence Laboratory, and its members created experimental programs including a screen-based text editor and Spacewar!. In 1984, journalist Steven Levy used the phrase "hacker ethic" for values he associated with this community.
Expansion beyond academic computing During the 1970s, less expensive microprocessors and personal-computer kits brought computing within reach of hobbyists outside universities, government laboratories, and large businesses. In Berkeley, Community Memory opened in 1973 as the first public computer-based bulletin board, giving people without previous computer access a place to exchange messages and information. The Homebrew Computer Club, founded in 1975, was a forum for hobbyists and experimenters, who shared ideas and demonstrated new hardware and software. The circulation of unauthorized copies of Altair BASIC led Microsoft founder Bill Gates to criticize hobbyists in a 1976 open letter. He argued that software copying deprived programmers of payment and discouraged the production of commercial software.
The personal-computer movement carried hacker culture into commercial software and the home video-game industry during the late 1970s and early 1980s. The GNU Project, begun in 1984, organized the development of a Unix-compatible operating system (OS) whose software could be run, copied, modified, and redistributed; GNU components were later combined with the Linux kernel to form a complete free OS.
Computer intrusion and the security meaning The computer underground emerged in the 1980s from telephone phreaking and from users who explored computer systems outside institutional settings. As home computers and modems spread, bulletin board systems connected participants in different cities. They exchanged technical information, login credentials, software, and news. Underground hackers formed groups and published electronic magazines; the Legion of Doom and Phrack became well-known examples.
Participants explored systems and learned technical methods; they also competed with one another and sought peer recognition. Some separated those activities from payment-card fraud and destructive attacks, but there was no agreed boundary. During the 1980s, reports of arrests and computer intrusions made hacker increasingly synonymous with a digital trespasser. Programmers continued to use the term positively within technical culture.
Public adoption and legal conflict The 1983 film WarGames brought computer intrusion to a mass audience and helped present hackers as a threat to national security. In the United States, Congress enacted the Computer Fraud and Abuse Act in 1986, creating federal offenses for specified forms of unauthorized access to protected computers. The Morris worm of 1988 disrupted a substantial part of the early Internet and led to the conviction of its creator Robert Tappan Morris in 1990, the first obtained under the act.
Operation Sundevil and related Secret Service investigations in 1990 targeted bulletin-board operators and people suspected of telecommunications and computer offenses. The raids and seizures raised questions about speech, privacy, and the legal treatment of electronic communications. The Electronic Frontier Foundation was founded in July that year after an investigation involving the publication of a telephone-system document, and it provided legal assistance in cases involving computer users and electronic communication.
Professionalization and institutionalization
During the 1990s, people from hacker and computer-underground communities began working in security consulting, software companies, and corporate research groups. Their knowledge of vulnerabilities became commercially useful. DEF CON, first held in 1993, and Black Hat, established in 1997, brought independent hackers into contact with security firms, technology vendors, government personnel, and law-enforcement officers. The Bugtraq mailing list, created in 1993, gave vulnerability finders a public forum for technical disclosures. It also allowed them to build professional reputations and pressured vendors to correct reported flaws. In 1998, members of L0pht Heavy Industries testified before the United States Senate as computer-security experts rather than criminal defendants.
Coordinated-disclosure policies and bug bounty programs later gave researchers formal ways to report vulnerabilities and work with affected organizations. Security tests that imitate attacks are generally carried out by penetration testers or white-hat hackers. In 2016, the United States Department of Defense ran Hack the Pentagon, the first bug-bounty program in the federal government. Eligible participants tested selected public websites under defined rules. The word retained conflicting meanings after professionalization: it described trusted security specialists and people regarded as computer-security threats.
Major traditions and communities Programmer and free-software hackers In the programmer tradition, hacking means understanding and modifying software. It also includes technically inventive ways to make a computer behave as intended or do something unexpected. Programmer hacking began in academic laboratories and spread to personal computing and commercial software. Open-source hacker communities disagree over proprietary software and the role of commercial businesses.