The information system enforces approved authorizations for logical access to the system in accordance with applicable policy.
Supplemental Guidance:
Access control policies (e.g., identity-based policies, role-based policies, attribute-based policies) and access enforcement mechanisms (e.g., access control lists, access control matrices, cryptography) are employed by organizations to control access between users (or processes acting on behalf of users) and objects (e.g., devices, files, records, processes, programs, domains) in the information system. In addition to enforcing authorized access at the information-system level, access enforcement mechanisms are employed at the application level, when necessary, to provide increased information security for the organization. Consideration is given to the implementation of an audited, explicit override of automated mechanisms in the event of emergencies or other serious events. If encryption of stored information is employed as an access enforcement mechanism, the cryptography used is FIPS 140-2 (as amended) compliant. For classified information, the cryptography used is largely dependent on the classification level of the information and the clearances of the individuals having access to the information. Mechanisms implemented by AC-3 are configured to enforce authorizations determined by other security controls. Related controls: AC-2, AC-4, AC-5, AC-6, AC-16, AC-17, AC-18, AC-19, AC-20, AC-21, AC-22, AU-9, CM-5, CM-6, MA-3, MA-4, MA-5, SA-7, SC-13, SI-9.
Control Enhancements:
(1) [Withdrawn: Incorporated into AC-6].
(2) The information system enforces dual authorization, based on organizational policies and procedures for [Assignment: organization-defined privileged commands].
Enchancement Supplemental Guidance:
Dual authorization mechanisms require two forms of approval to execute. The organization does not employ dual authorization mechanisms when an immediate response is necessary to ensure public and environmental safety.
(3) The information system enforces [Assignment: organization-defined nondiscretionary access control policies] over [Assignment: organization-defined set of users and resources] where the policy rule set for each policy specifies:
    (a) Access control information (i.e., attributes) employed by the policy rule set (e.g., position, nationality, age, project, time of day); and
    (b) Required relationships among the access control information to permit access.
Enchancement Supplemental Guidance:
Nondiscretionary access control policies that may be implemented by organizations include, for example, Attribute-Based Access Control, Mandatory Access Control, and Originator Controlled Access Control. Nondiscretionary access control policies may be employed by organizations in addition to the employment of discretionary access control policies.

For Mandatory Access Control (MAC): Policy establishes coverage over all subjects and objects under its control to ensure that each user receives only that information to which the user is authorized access based on classification of the information, and on user clearance and formal access authorization. The information system assigns appropriate security attributes (e.g., labels/security domains/types) to subjects and objects, and uses these attributes as the basis for MAC decisions. The Bell-LaPadula security model defines allowed access with regard to an organization-defined set of strictly hierarchical security levels as follows: A subject can read an object only if the security level of the subject dominates the security level of the object and a subject can write to an object only if two conditions are met: the security level of the object dominates the security level of the subject, and the security level of the user's clearance dominates the security level of the object (no read up, no write down).

For Role-Based Access Control (RBAC): Policy establishes coverage over all users and resources to ensure that access rights are grouped by role name, and access to resources is restricted to users who have been authorized to assume the associated role.
(4) The information system enforces a Discretionary Access Control (DAC) policy that:
    (a) Allows users to specify and control sharing by named individuals or groups of individuals, or by both;
    (b) Limits propagation of access rights; and
    (c) Includes or excludes access to the granularity of a single user.
(5) The information system prevents access to [Assignment: organization-defined security-relevant information] except during secure, nonoperable system states.
Enchancement Supplemental Guidance:
Security-relevant information is any information within the information system that can potentially impact the operation of security functions in a manner that could result in failure to enforce the system security policy or maintain isolation of code and data. Filtering rules for routers and firewalls, cryptographic key management information, key configuration parameters for security services, and access control lists are examples of security-relevant information. Secure, nonoperable system states are states in which the information system is not performing mission/business-related processing (e.g., the system is off-line for maintenance, troubleshooting, boot-up, shutdown).
(6) The organization encrypts or stores off-line in a secure location [Assignment: organization-defined user and/or system information].
Enchancement Supplemental Guidance:
The use of encryption by the organization reduces the probability of unauthorized disclosure of information and can also detect unauthorized changes to information. Removing information from online storage to offline storage eliminates the possibility of individuals gaining unauthorized access via a network. Related control: MP-4.
Priority and Baseline Allocation:

P1 LOW   AC-3 MOD   AC-3 HIGH   AC-3

ISO/IEC 27001 Annex A Control Mapping:
A.10.8.1  Information exchange policies and procedures
A.11.4.4  Remote diagnostic and configuration port protection
A.11.4.6  Network connection control
A.11.5.4  Use of system utilities
A.11.6.1  Information access restriction
A.12.4.2  Protection of system test data





















NIST Special Publication 800-53: This publication may be used by nongovernmental organizations on a voluntary basis and is not subject to copyright in the United States.
Attribution would, however, be appreciated by NIST.

This document was produced from an export of the database beta application released with NIST SP 800-53 REV 3.
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Tim Hudson -