Detecting an attack on an authentication service. A first memory area is configured to store data relating to a plurality of requests communicated to an authentication service from a plurality of user agents. A second memory area is configured to store a predefined pattern of one or more requests. The predefined pattern characterizes an attack. A processor searches the stored data as a function of a query variable to identify at least one of the plurality of the requests communicated from at least one of the plurality of the user agents and compares the stored data associated with each of the identified requests with the predefined pattern to determine whether the identified request indicates the attack characterized by the predefined pattern. Other aspects of the invention are directed to computer-readable media for use with detecting the attack on the authentication service.