A hacker is a person skilled in information technology who achieves goals by non-standard means. The term has become associated in popular culture with a security hacker – someone with knowledge of bugs or exploits to break into computer systems and access data which would otherwise be inaccessible to them. In a positive connotation, though, hacking can also be utilized by legitimate figures in legal situations. For example, law enforcement agencies sometimes use hacking techniques to collect evidence on criminals and other malicious actors. This could include using anonymity tools to mask their identities online and pose as criminals. Likewise, covert world agencies can employ hacking techniques in the legal conduct of their work. Hacking and cyber-attacks are used extra-legally and illegally by law enforcement and security agencies, and employed by state actors as a weapon of legal and illegal warfare.

Phreaking is a slang term coined to describe the activity of a culture of people who study, experiment with, or explore telecommunication systems, such as equipment and systems connected to public telephone networks. The term phreak is a sensational spelling of the word freak with the ph- from phone, and may also refer to the use of various audio frequencies to manipulate a phone system. Phreak, phreaker, or phone phreak are names used for and by individuals who participate in phreaking.