Any general mechanism that controls access to resources using roles instead of user credentials.
Role-based security is at the heart of many platforms and products including Microsoft Windows operating systems. The architecture of Microsoft Windows NT uses role-based security based on privileges assigned to local groups such as Administrators, Users, and Guests. By simply making a user a member of one of these groups, the user assumes the role of the generic group member and has all the rights to perform system tasks and permissions to access resources that belong to the group. Microsoft Transaction Server (MTS), and later COM+, enhanced this role-based security approach by providing developers with ways of defining their own abstract roles for use with custom-developed applications.
Administrators could then assign users to specific roles to define levels of access to distributed applications and resources on a network. The Microsoft .NET Framework extends this model further by including support for role-based authorization within the common language runtime based on Windows accounts or custom identities.