In the computer security context, a hacker is someone who seeks and exploits weaknesses in a computer system or computer network. Hackers may be motivated by a multitude of reasons, such as profit, protest, challenge, enjoyment, or to evaluate those weaknesses to assist in removing them. The subculture that has evolved around hackers is often referred to as the computer underground and is now a known community. While other uses of the word hacker exist that are not related to computer security, such as referring to someone with an advanced understanding of computers and computer networks, they are rarely used in mainstream context. They are subject to the longstanding hacker definition controversy about the term's true meaning. In this controversy, the term hacker is reclaimed by computer programmers who argue that someone who breaks into computers, whether computer criminal (black hats) or computer security expert (white hats), is more appropriately called a cracker instead. Some white hat hackers claim that they also deserve the title hacker, and that only black hats should be called "crackers".

En sécurité informatique, un (ou hackeur) est une personne qui recherche les moyens de contourner les protections logicielles et matérielles. Il y a différents types de hackers en sécurité informatique, le white hat (chapeau blanc) est un hacker éthique ou un expert en sécurité informatique son but est de signaler les failles trouvées au propriétaire du système concerné (dans une démarche d'amélioration de la sécurité de ce système), ne pas confondre avec le black hat (chapeau noir) qui lui va en tirer profit, les utiliser dans une démarche militante (on parle alors d'hacktivisme), les revendre ou simplement considérer le contournement () comme un défi, il y a aussi le grey hat lui est entre le white et black hat.