The security mechanism determining and enforcing what authenticated users are authorized to do within a computer system. The dominant forms of authorization are DAC, MAC and RBAC. DAC (Discretionary Access Control) manages access using ACL (Access Control Lists) on each resource object where users are listed along with the permissions or privileges granted or denied them. MAC (Mandatory Access Control) manages access using labels of classification or clearance on both subjects and objects, and only those subjects with equal or superior clearance are allowed to access resources. RBAC (Role Based Access Control) manages access using labels of a job role that has been granted the permissions and privileges needed to accomplish a specific job or role.