1. A method, performed by a first computing system having a processor, for authenticating a user of a first application executing at a second computing system, the method comprising: establishing a user account with an operating system executing at the first computing system and configured to manage access to a first resource; receiving, from the second computing system, a request to authenticate a user, the request including credentials; requesting access to the first resource using the established user account and the received credentials; and sending, to the second computing system, an indication of whether the first resource was successfully accessed using the established account and the received credentials, wherein authentication of the user is based at least in part on whether the resource was successfully accessed at the first computing system using the established account and the received credentials.