Continued secure access to computer system maintained by periodic challenge-response

摘要

An entity 210, 220 requesting communications access to the system 100 is sent a first challenge message. Access is denied unless a first response matches a predetermined, authorised user, allowing a second challenge message to be sent. If a second response comprises a predetermined sequence of codes or numbers, access is allowed. If the second response does not match the sequence, access is denied and the second challenge is re-sent. Communication with the entity is terminated after a predetermined number of successive mismatches. If the entity is granted access, further challenges are issued periodically. If a further response matches a predetermined sequence, continued access is granted. If a further response does not match the sequence the further challenge is re-sent until, after a predetermined number of successive mismatches, communications access is terminated. Typically, the computer system is for equipment monitoring and diagnostics. Preferably, the first challenge comprises a predetermined code or number. Preferably a further challenge is issued at least once every predetermined period of real time. In an embodiment, an authentication challenge application (ACA, 200) of the system communicates with an authentication response application (ARA) of a user device over a communication network.