ac-20-4-network-accessible-storage-devices-prohibited-use

name	AC-20(4)_network-accessible-storage-devices-prohibited-use
description	Prohibit the use of [organization-defined] in external systems.
category	authorization
version	5.2.0
author	cyberstrike-official
tags	["nist","sp800-53","rev5","ac-20-4","ac","enhancement"]
tech_stack	["aws","azure","gcp","linux","windows"]
cwe_ids	["CWE-284"]
chains_with	[]
prerequisites	["AC-20"]
severity_boost	{}

AC-20(4) Network Accessible Storage Devices — Prohibited Use

Enhancement of: AC-20

High-Level Description

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

Network-accessible storage devices in external systems include online storage devices in public, hybrid, or community cloud-based systems.

What to Check

• Verify AC-20(4) Network Accessible Storage Devices — Prohibited Use is documented in SSP
• Confirm control is operating effectively
• Review evidence of continuous monitoring for AC-20(4)
• Verify enhancement builds upon base control AC-20

How to Test

Step 1: Review Documentation

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

Prohibit the use of [organization-defined] in external systems.

Implementation Guidance

Network-accessible storage devices in external systems include online storage devices in public, hybrid, or community cloud-based systems.

Risk Assessment

Finding	Severity	Impact
AC-20(4) Network Accessible Storage Devices — Prohibited Use not implemented