AC-4(20)_approved-solutions

AC-4(20) Approved Solutions

Enhancement of: AC-4

High-Level Description

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

Organizations define approved solutions and configurations in cross-domain policies and guidance in accordance with the types of information flows across classification boundaries. The National Security Agency (NSA) National Cross Domain Strategy and Management Office provides a listing of approved cross-domain solutions. Contact ncdsmo@nsa.gov for more information.

What to Check

• Verify AC-4(20) Approved Solutions is documented in SSP
• Confirm control is operating effectively
• Review evidence of continuous monitoring for AC-4(20)
• Verify enhancement builds upon base control AC-4

How to Test

Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for AC-4(20) 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

Employ [organization-defined] to control the flow of [organization-defined] across security domains.

Implementation Guidance

Organizations define approved solutions and configurations in cross-domain policies and guidance in accordance with the types of information flows across classification boundaries. The National Security Agency (NSA) National Cross Domain Strategy and Management Office provides a listing of approved cross-domain solutions. Contact ncdsmo@nsa.gov for more information.

Risk Assessment

CWE Categories

References

• NIST SP 800-53 Rev 5 - AC-4(20)
• 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 (none) reviewed