Authorization (computer access control)

Authorization is the function of specifying access rights to resources related to information security and computer security in general and to access control in particular. More formally, "to authorize" is to define an access policy. For example, human resources staff is normally authorized to access employee records and this policy is usually formalized as access control rules in a computer system. During operation, the system uses the access control rules to decide whether access requests from (authenticated) consumers shall be approved (granted) or disapproved (rejected). Resources include individual files or an item's data, computer programs, computer devices and functionality provided by computer applications. Examples of consumers are computer users, computer Software and other Hardware on the computer.

Access control in computer systems and networks rely on access policies. The access control process can be divided into the following phases: policy definition phase where access is authorized, and policy enforcement phase where access requests are approved or disapproved. Authorization is the function of the policy definition phase which precedes the policy enforcement phase where access requests are approved or disapproved based on the previously defined authorizations.

Most modern, multi-user operating systems include access control and thereby rely on authorization. Access control also uses authentication to verify the identity of consumers. When a consumer tries to access a resource, the access control process checks that the consumer has been authorized to use that resource. Authorization is the responsibility of an authority, such as a department manager, within the application domain, but is often delegated to a custodian such as a system administrator. Authorizations are expressed as access policies in some types of "policy definition application", e.g. in the form of an access control list or a capability, on the basis of the "principle of least privilege": consumers should only be authorized to access whatever they need to do their jobs. Older and single user operating systems often had weak or non-existent authentication and access control systems.

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