Anonymisation is an irreversible modification of data after which a specific individual can no longer be identified by any reasonably available means. Such data ceases to be personal data, and protection rules no longer apply to it. Pseudonymisation replaces identifiers with a substitute key, but re-identification remains possible with access to additional information – it therefore still counts as personal data, just at lower risk. Companies often confuse these terms and consider replacing a name to be anonymisation, even though it is not. The practical consequence is significant: pseudonymised data must still be protected, recorded and deleted according to retention periods. Genuine anonymisation is difficult especially with small samples, where an individual can be inferred from a combination of data points.
See also: Privacy policy, Data retention and deletion, Data quality in analytics.
