AC-3(3)_mandatory-access-control

AC-3(3) Mandatory Access Control

Enhancement of: AC-3

High-Level Description

Family: Access Control (AC) Framework: NIST SP 800-53 Rev 5

Mandatory access control is a type of nondiscretionary access control. Mandatory access control policies constrain what actions subjects can take with information obtained from objects for which they have already been granted access. This prevents the subjects from passing the information to unauthorized subjects and objects. Mandatory access control policies constrain actions that subjects can take with respect to the propagation of access control privileges; that is, a subject with a privilege cannot pass that privilege to other subjects. The policy is uniformly enforced over all subjects and objects to which the system has control. Otherwise, the access control policy can be circumvented. This enforcement is provided by an implementation that meets the reference monitor concept as described in AC-25 . The policy is bounded by the system (i.e., once the information is passed outside of the control of the system, additional means may be required to ensure that the constraints on the information remain in effect).

The trusted subjects described above are granted privileges consistent with the concept of least privilege (see AC-6 ). Trusted subjects are only given the minimum privileges necessary for satisfying organizational mission/business needs relative to the above policy. The control is most applicable when there is a mandate that establishes a policy regarding access to controlled unclassified information or classified information and some users of the system are not authorized access to all such information resident in the system. Mandatory access control can operate in conjunction with discretionary access control as described in AC-3(4) . A subject constrained in its operation by mandatory access control policies can still operate under the less rigorous constraints of AC-3(4), but mandatory access control policies take precedence over the less rigorous constraints of AC-3(4). For example, while a mandatory access control policy imposes a constraint that prevents a subject from passing information to another subject operating at a different impact or classification level, AC-3(4) permits the subject to pass the information to any other subject with the same impact or classification level as the subject. Examples of mandatory access control policies include the Bell-LaPadula policy to protect confidentiality of information and the Biba policy to protect the integrity of information.

What to Check

• Verify AC-3(3) Mandatory Access Control is documented in SSP
• Validate all 8 control requirements are implemented
• Confirm control is operating effectively
• Review evidence of continuous monitoring for AC-3(3)
• Verify enhancement builds upon base control AC-3

How to Test

Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for AC-3(3) implementation details. Verify the organization has documented how this control is satisfied.

Step 2: Validate Implementation

# For cloud environments, use cloud-audit-mcp tools
# For on-premises, review system configurations directly

# Example: Check if account management policies exist
grep -r "account.management\|access.control" /etc/security/ 2>/dev/null

Step 3: Test Operating Effectiveness

Verify the control is actively functioning, not just documented. Check logs, configurations, and operational evidence.

Tools

Remediation Guide

Control Statement

Enforce [organization-defined] over the set of covered subjects and objects specified in the policy, and where the policy: Is uniformly enforced across the covered subjects and objects within the system; Specifies that a subject that has been granted access to information is constrained from doing any of the following; Passing the information to unauthorized subjects or objects; Granting its privileges to other subjects; Changing one or more security attributes (specified by the policy) on subjects, objects, the system, or system components; Choosing the security attributes and attribute values (specified by the policy) to be associated with newly created or modified objects; and Changing the rules governing access control; and Specifies that [organization-defined] may explicitly be granted [organization-defined] such that they are not limited by any defined subset (or all) of the above constraints.

Implementation Guidance

Mandatory access control is a type of nondiscretionary access control. Mandatory access control policies constrain what actions subjects can take with information obtained from objects for which they have already been granted access. This prevents the subjects from passing the information to unauthorized subjects and objects. Mandatory access control policies constrain actions that subjects can take with respect to the propagation of access control privileges; that is, a subject with a privilege cannot pass that privilege to other subjects. The policy is uniformly enforced over all subjects and objects to which the system has control. Otherwise, the access control policy can be circumvented. This enforcement is provided by an implementation that meets the reference monitor concept as described in AC-25 . The policy is bounded by the system (i.e., once the information is passed outside of the control of the system, additional means may be required to ensure that the constraints on the information remain in effect).

The trusted subjects described above are granted privileges consistent with the concept of least privilege (see AC-6 ). Trusted subjects are only given the minimum privileges necessary for satisfying organizational mission/business needs relative to the above policy. The control is most applicable when there is a mandate that establishes a policy regarding access to controlled unclassified information or classified information and some users of the system are not authorized access to all such information resident in the system. Mandatory access control can operate in conjunction with discretionary access control as described in AC-3(4) . A subject constrained in its operation by mandatory access control policies can still operate under the less rigorous constraints of AC-3(4), but mandatory access control policies take precedence over the less rigorous constraints of AC-3(4). For example, while a mandatory access control policy imposes a constraint that prevents a subject from passing information to another subject operating at a different impact or classification level, AC-3(4) permits the subject to pass the information to any other subject with the same impact or classification level as the subject. Examples of mandatory access control policies include the Bell-LaPadula policy to protect confidentiality of information and the Biba policy to protect the integrity of information.

Risk Assessment

CWE Categories

References

• NIST SP 800-53 Rev 5 - AC-3(3)
• NIST SP 800-53A Rev 5 (Assessment Procedures)
• NIST SP 800-53 Rev 5 Full Catalog

Checklist

• Control documented in SSP
• Implementation evidence collected
• Operating effectiveness validated
• Continuous monitoring in place
• Related controls (SC-7) reviewed