Abstract: A method, implemented by a computer-implemented authentication system, for authenticating a user attempting to access a target component of a computer system, the method comprising: a) receiving, from a first user system via a computer network, user authentication information and a network address identifying the first user system within the computer network; b) obtaining at least one data item of contextual information indicative of a property of an environment of a wireless communications device associated with the user authentication information; c) authenticating the user based on at least the user authentication information; and d) subject to successful authentication, granting access to the target component and storing a data record comprising the received network address and the received contextual information.