PROVIDING REMOTE USER AUTHENTICATION

Providing a remote computer user authentication service involves providing a reference to a user authentication service in a host server's source code (e.g., website source code). Further, integration code that may be used in an application programming interface (API) on the host server for interaction with a user authentication service can be provided. Additionally, a user interface (UI) for user authentication on the host server, and an authentication-test message on the host server using the UI may be provided. Also, providing authentication can comprise sending an authentication-request message to a mobile device designated by the user; and/or can comprise the user responding with information from the authentication-test message. The host server can be notified of the user's authentication after a correct response is received by the user authentication service.