A leak is the unauthorized release of information, files, or other sensitive material. In cyber security, a leak can expose credentials, source code, customer data, private messages, or internal documents. Once released, the material may be copied, indexed, mirrored, or shared beyond the attacker’s control, making the impact difficult to reverse.
Leaks matter because they can enable account takeover, fraud, espionage, extortion, and reputational harm. In real attacks, leaks often happen after data theft, insider misuse, misconfigured storage, or poor access control. Defenders try to prevent and limit leaks with least-privilege access, encryption, logging, data loss prevention tools, and rapid credential rotation. When a leak occurs, fast containment and evidence preservation help reduce harm and support investigation.