Authenticating an end user for a client application using a directory service can include receiving end user identity information and security information at the client application, sending a search request to the directory service for an entry associated with the end user identity information and, if a match is found, receiving a authentication token from the directory service associated with the end user identity information. The received authentication token can be compared with the security information. If the authentication token matches the security information, sending a request to update the directory service to indicate that successful authentication of the end user has occurred and if the authentication token does not match the security information, sending a request to update the directory service to indicate that a failed attempt at authentication of the end user has occurred.