A personal data breach is a a breach of security leading to the accidental or unlawful destruction, loss, alteration, unauthorised disclosure of, or access to, personal data transmitted, stored or otherwise processed;

Data breaches can be categorised according to 3 well-known information security principles:

• confidentiality breach: the unauthorised or accidental disclosure of, or access to, personal data;
• availability breach: the unauthorised or accidental loss of access to, or destruction of, personal data;
• integrity breach: the unauthorised or accidental alteration of personal data;

Depending on circumstances, a breach can concern confidentiality, integrity and availability of personal data at the same time, as well as any combination of these.