AC 4(2) Processing Domains

---
name: "AC-4(2)_processing-domains"
description: "Use protected processing domains to enforce [organization-defined] as a basis for flow control decisions."
category: "authorization"
version: "5.2.0"
author: "cyberstrike-official"
tags:
  - nist
  - sp800-53
  - rev5
  - ac-4-2
  - ac
  - enhancement
tech_stack:
  - aws
  - azure
  - gcp
  - linux
  - windows
cwe_ids:
  - CWE-284
chains_with:
  - SC-39
prerequisites:
  - AC-4
severity_boost:
  SC-39: "Chain with SC-39 for comprehensive security coverage"
---

# AC-4(2) Processing Domains

> **Enhancement of:** AC-4

## High-Level Description

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

Protected processing domains within systems are processing spaces that have controlled interactions with other processing spaces, enabling control of information flows between these spaces and to/from information objects. A protected processing domain can be provided, for example, by implementing domain and type enforcement. In domain and type enforcement, system processes are assigned to domains, information is identified by types, and information flows are controlled based on allowed information accesses (i.e., determined by domain and type), allowed signaling among domains, and allowed process transitions to other domains.

## What to Check

- [ ] Verify AC-4(2) Processing Domains is documented in SSP
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for AC-4(2)
- [ ] 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(2) 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 | Test web application access controls   | `hackbrowser`        |

## Remediation Guide

### Control Statement

Use protected processing domains to enforce [organization-defined] as a basis for flow control decisions.

### Implementation Guidance

Protected processing domains within systems are processing spaces that have controlled interactions with other processing spaces, enabling control of information flows between these spaces and to/from information objects. A protected processing domain can be provided, for example, by implementing domain and type enforcement. In domain and type enforcement, system processes are assigned to domains, information is identified by types, and information flows are controlled based on allowed information accesses (i.e., determined by domain and type), allowed signaling among domains, and allowed process transitions to other domains.

## Risk Assessment

| Finding                                    | Severity | Impact                    |
| ------------------------------------------ | -------- | ------------------------- |
| AC-4(2) Processing Domains not implemented | High     | Access Control            |
| AC-4(2) partially implemented              | Medium   | Incomplete Access Control |

## CWE Categories

| CWE ID  | Title                   |
| ------- | ----------------------- |
| CWE-284 | Improper Access Control |

## References

- [NIST SP 800-53 Rev 5 - AC-4(2)](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=ac-4.2)
- [NIST SP 800-53A Rev 5 (Assessment Procedures)](https://csrc.nist.gov/pubs/sp/800/53/a/r5/final)
- [NIST SP 800-53 Rev 5 Full Catalog](https://csrc.nist.gov/pubs/sp/800/53/r5/upd1/final)

## Checklist

- [ ] Control documented in SSP
- [ ] Implementation evidence collected
- [ ] Operating effectiveness validated
- [ ] Continuous monitoring in place
- [ ] Related controls (SC-39) reviewed