Active Directory Federation Services (ADFS or AD FS), a software component developed by Microsoft, can run on Windows Server operating systems to provide users with single sign-on access to systems and applications located across organizational boundaries. It uses a  claims-based access-control authorization model to maintain application security and to implement federated identity. (Claims-based authentication involves authenticating a user based on a set of claims about that user's identity contained in a trusted token. Such a token is often issued and signed by an entity that is able to authenticate the user by other means, and that is trusted by the entity doing the claims-based authentication.) It is part of the Active Directory Services.