A system and method of authentication is provided that uses the spatiotemporal context of a user which has been measured using third party monitoring systems. Spatiotemporal data obtained from third party systems such as CCTV networks, microphone networks, UAV networks, CAV networks, ATM networks or the like is used to determine a unique spatiotemporal fingerprint for an individual. That is, the unique identifier is not derived from a device carried by the individual. This fingerprint can then be used to verify a user and detect abnormal and unexpected behaviour.