| name | AC-4(21)_physical-or-logical-separation-of-information-flows |
| description | Separate information flows logically or physically using [organization-defined] to accomplish [organization-defined]. |
| category | authorization |
| version | 5.2.0 |
| author | cyberstrike-official |
| tags | ["nist","sp800-53","rev5","ac-4-21","ac","enhancement"] |
| tech_stack | ["aws","azure","gcp","linux","windows"] |
| cwe_ids | ["CWE-284"] |
| chains_with | ["SC-32"] |
| prerequisites | ["AC-4"] |
| severity_boost | {"SC-32":"Chain with SC-32 for comprehensive security coverage"} |
AC-4(21) Physical or Logical Separation of Information Flows
Enhancement of: AC-4
High-Level Description
Family: Access Control (AC)
Framework: NIST SP 800-53 Rev 5
Enforcing the separation of information flows associated with defined types of data can enhance protection by ensuring that information is not commingled while in transit and by enabling flow control by transmission paths that are not otherwise achievable. Types of separable information include inbound and outbound communications traffic, service requests and responses, and information of differing security impact or classification levels.
What to Check
How to Test
Step 1: Review Documentation
Examine the System Security Plan (SSP) and related artifacts for AC-4(21) 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
| Tool | Purpose | Usage |
|---|
| cloud-audit-mcp | Check IAM policies and access controls | cloud_audit_iam_policies |
| hackbrowser-mcp | Test web application access controls | browser_auth_test |
Remediation Guide
Control Statement
Separate information flows logically or physically using [organization-defined] to accomplish [organization-defined].
Implementation Guidance
Enforcing the separation of information flows associated with defined types of data can enhance protection by ensuring that information is not commingled while in transit and by enabling flow control by transmission paths that are not otherwise achievable. Types of separable information include inbound and outbound communications traffic, service requests and responses, and information of differing security impact or classification levels.
