# NIST SP 800-53 Rev. 5 AC-4(20) — Approved Solutions - Source: https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-4-20-approved-solutions - 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-4(20)`·critical·Component: **Access Control** ## What this control requires > Organizations must employ defined solutions in approved configurations to control the flow of specified information across security domains. These solutions and configurations are outlined in cross-domain policies and guidance, tailored to the types of information flows across classification boundaries. This control supports the Governance capability within the Access Control family. > > — NIST SP 800-53 Rev. 5, Control AC-4(20) ### In plain English Organizations must employ defined solutions in approved configurations to control the flow of specified information across security domains. 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-4(20)) 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. - **Information.** Document the trigger, the owner and the cadence. - **Security.** Document the trigger, the owner and the cadence. - **Domain.** Document the trigger, the owner and the cadence. - **Scope:** management, access control, information, domains, solutions, 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: Approved Solutions. ## 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) 164.308(a)(4)(ii)(A)** — Information Access Management - Isolating Healthcare Clearinghouse Functions](https://support.icompaas.com/compliance/hipaa/164-308-a-4-ii-a-information-access-management-isolating-healthcare-clearinghouse) - [**ISO/IEC 27001:2022 A.5.1** — Policies for information security](https://support.icompaas.com/compliance/iso-27001-2022/a-5-1-policies-for-information-security) - [**BSI C5:2020 SP-01** — Documentation, communication and provision of policies and instructions](https://support.icompaas.com/compliance/bsi-c5-2020/sp-01-documentation-communication-and-provision-of-policies-and-instructions) - [**ISO/IEC 27701:2025 A.3.3** — Information security policies](https://support.icompaas.com/compliance/iso-27701-2025/a-3-3-information-security-policies) ## Related controls in NIST SP 800-53 Rev. 5 - [**Control AC-4(27)** — Redundant/Independent Filtering Mechanisms](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-4-27-redundant-independent-filtering-mechanisms) - [**Control AC-4(24)** — Internal Normalized Format](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-4-24-internal-normalized-format) - [**Control AC-4(26)** — Audit Filtering Actions](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-4-26-audit-filtering-actions) - [**Control AC-4(30)** — Filter Mechanisms Using Multiple Processes](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-4-30-filter-mechanisms-using-multiple-processes) - [**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(2)** — Processing Domains](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ac-4-2-processing-domains) ## 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-4(20)` 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.