Abstract: The invention concerns a network policy controller coupled to a computer network and including a communications interface (303) arranged to monitor network authorization requests relating to a plurality of network devices connected to said network; at least one memory (306) arranged to store past network authorization requests relating to each of said plurality of network devices; and a processor (302) arranged to verify, in response to a network authorization request relating to one of said network devices, the occurrence of at least one past network authorization request stored in said memory for said network device, and to perform an action based on said verification.