1. A method of controlling access to a network resource, comprising: receiving a request to access to the network resource, the request including a user identifier; determining whether the received user identifier is stored in a user data store associated with the resource; and where it is not so determined: determining, from user details stored in a master user data store, whether the user is authorized to access the resource; and where it is so determined: obtaining a password; and storing the obtained password and user details in the data store associated with the network resource.