# NIST SP 800-53 Rev. 5 AC-3(15) — Discretionary And Mandatory Access Control - Source: https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-3-15-discretionary-and-mandatory-access-control - Section: [Compliance](https://support.icompaas.com/compliance) › [NIST SP 800-53 Rev. 5 Controls](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5) › AC — Access Control - Last updated: 2026-06-05 - Publisher: iCompaas, Inc. (https://www.icompaas.com) **NIST SP 800-53 Rev. 5**·Control `AC-3(15)`·critical·Component: **Access Control** ## What this control requires > Organizations must enforce both a mandatory access control (MAC) policy and a discretionary access control (DAC) policy over the defined subjects and objects in the system. Implementing both policies provides additional protection against unauthorized code execution by users or processes, preventing a single compromised user or process from affecting the entire system. This control supports the Governance capability within the Access Control family. > > — NIST SP 800-53 Rev. 5, Control AC-3(15) ### In plain English Organizations must enforce both a mandatory access control (MAC) policy and a discretionary access control (DAC) policy over the defined subjects and objects in the system. In practice, this means you can prove you policy management-level controls on a defined cadence. ## Why it matters SP 800-53 is the catalogue every U.S. federal authorisation (FedRAMP, FISMA, CMMC) and most regulated industries point at. A missing control surfaces as a Plan of Action & Milestones (POA&M) item that an Authorizing Official must approve before the Authority To Operate is granted or renewed. This control is rated **critical** in the source catalogue. Treat gaps here as production incidents in the risk register, not housekeeping. ## What an auditor looks for A 3PAO (FedRAMP) or Independent Assessor (NIST RMF) tests against NIST SP 800-53A assessment procedures. For each control they expect a documented implementation that addresses every assessment objective (Examine, Interview, Test) and an implementation summary in the System Security Plan. Within **Access Control**, the assessor will trace your implementation back to the catalogue reference (Control AC-3(15)) and look for objective evidence on the latest two assessment cycles. ## How to implement #### Policy Management **Docs.** Keep each policy in version-controlled Markdown alongside the code that implements it; ship a signed PDF snapshot at each annual review and link the SHA into the SoA. ### Operational checklist - **Policy.** Document the trigger, the owner and the cadence. - **Access.** Document the trigger, the owner and the cadence. - **Mandatory.** Document the trigger, the owner and the cadence. - **Discretionary.** Document the trigger, the owner and the cadence. - **Process.** Document the trigger, the owner and the cadence. - **Scope:** management, access control, mandatory access control, system, protection, capability, organizations, policy. ## Evidence to collect - **Policy Document.** A signed and version-controlled policy / standard / procedure document. Signed policy or standard documents the safeguard. Focus: Discretionary And Mandatory Access Control. ## Common pitfalls - Policies that no engineer has read; the version in Confluence drifts from the version that's actually being enforced. ## How it maps to other frameworks Computed from shared tags, control component and key-operation subjects — handy when you are reconciling controls across an audit. - [**NIST SP 800-171 Rev. 3 3.1.5** — Least Privilege](https://support.icompaas.com/compliance/nist-sp-800-171-rev-3/3-1-5-least-privilege) - [**HIPAA (45 CFR Part 164) 164.310(a)(2)(iii)** — Facility Access Controls - Access Control and Validation Procedures](https://support.icompaas.com/compliance/hipaa/164-310-a-2-iii-facility-access-controls-access-control-and-validation-procedures) - [**BSI C5:2020 AM-02** — Acceptable Use and Safe Handling of Assets Policy](https://support.icompaas.com/compliance/bsi-c5-2020/am-02-acceptable-use-and-safe-handling-of-assets-policy) ## Related controls in NIST SP 800-53 Rev. 5 - [**Control AC-3(3)** — Mandatory Access Control](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-3-3-mandatory-access-control) - [**Control AC-4(5)** — Embedded Data Types](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-4-5-embedded-data-types) - [**Control AC-4(4)** — Flow Control Of Encrypted Information](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-4-4-flow-control-of-encrypted-information) - [**Control AC-3(4)** — Discretionary Access Control](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-3-4-discretionary-access-control) - [**Control AC-4(20)** — Approved Solutions](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-4-20-approved-solutions) - [**Control AC-6** — Least Privilege](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-6-least-privilege) ## References - [NIST Computer Security Resource Center — NIST SP 800-53 Rev. 5](https://csrc.nist.gov/Projects/risk-management/sp800-53-controls) - Catalogue identifier: `Control AC-3(15)` Topics: governance riskpolicy management ## Related compliance guidance - [NIST SP 800-53 Rev. 5: a practical implementation guide for cloud teams](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5): Start with the full NIST SP 800-53 implementation guide — scope, roadmap, evidence and how the assessment runs. - [NIST SP 800-171 and CMMC: a practical guide to protecting CUI in the cloud](https://support.icompaas.com/compliance/nist-sp-800-171-rev-3): If your obligation is protecting CUI in your own systems for a federal or defence contract, this derived subset — not the full catalogue — is the requirement. - [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Most commercial SaaS already hold a SOC 2 Type 2, and FedRAMP 20x Class A is designed for providers that have one.