Classification levels define the sensitivity categories applied to information assets, typically ranging from public (freely shareable) through internal (for employees only) and confidential (restricted access) to secret (highest sensitivity). Each level prescribes specific handling, storage, transmission and disposal requirements.
Establishing clear classification levels is a foundational requirement of ISO 27001 and enables organisations to apply the principle of proportionality: more sensitive data receives stronger controls, while less sensitive data avoids unnecessary overhead. Consistent classification also supports access control decisions, data loss prevention policies and regulatory compliance for frameworks such as GDPR and NIS2.