Data breach

A data breach is a security violation. It causes all sensitive, protected or confidential data to be copied, transmitted, viewed, stolen or used by an unauthorized person or organisation. This term is known as unintentional information disclosure, data leak, information leakage, and data spill. A deliberate data breach by a person privy to the information, typically for political purposes, is more often known as a "leak".
Data breaches may involve financial information such as credit card and debit card details, bank details, personal health information (PHI), Personally identifiable information (PII), trade secrets of corporations or intellectual property. Data breaches may involve overexposed and vulnerable unstructured data – files, documents, and sensitive information.
Data breaches can be quite costly to organizations with direct costs (remediation, investigation, etc) and indirect costs (reputational damages, providing cyber security to victims of compromised data, etc.).
ISO/IEC 27040 defines a data breach as: "compromise of security that leads to the accidental or unlawful destruction, loss, alteration, unauthorized disclosure of, or access to protected data transmitted, stored or otherwise processed".