# Boundary Protection (03.13.01)_boundary-protection

> Monitor and control communications at external managed interfaces to the system and key internal managed interfaces within the system.

- Skill: `cyberstrikeus/boundary-protection-03-13-01-boundary-protection` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/boundary-protection-03-13-01-boundary-protection`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/boundary-protection-03-13-01-boundary-protection/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/boundary-protection-03-13-01-boundary-protection

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# Boundary Protection (03.13.01) Boundary Protection

## High-Level Description

**Family:** System and Communications Protection
**Framework:** NIST SP 800-171 Rev 3
**Applicability:** Systems processing, storing, or transmitting CUI

Monitor and control communications at external managed interfaces to the system and key internal managed interfaces within the system.
Implement subnetworks for publicly accessible system components that are physically or logically separated from internal networks.
Connect to external systems only through managed interfaces that consist of boundary protection devices arranged in accordance with an organizational security architecture.

## What to Check

- [ ] Verify Boundary Protection (03.13.01) Boundary Protection is implemented for CUI systems
- [ ] Review SSP documentation for Boundary Protection (03.13.01)
- [ ] Validate CMMC Level 2 assessment objective for Boundary Protection (03.13.01)
- [ ] Confirm POA&M addresses any gaps for Boundary Protection (03.13.01)

## How to Test

### Step 1: Review System Security Plan

Examine the SSP for Boundary Protection (03.13.01) implementation description and responsible parties.

### Step 2: Assess Implementation

```
# Verify security controls protecting CUI
# Check access controls, encryption, monitoring as applicable

# For Linux systems:
ls -la /etc/security/ 2>/dev/null
grep -r "CUI\|controlled" /etc/security/ 2>/dev/null

# For cloud:
# Use cloud-audit-mcp tools to assess posture
```

### Step 3: CMMC Assessment Validation

Verify this requirement passes CMMC Level 2 assessment methodology per SP 800-171A Rev 3.

## Tools

| Tool            | Purpose                      | Usage                  |
| --------------- | ---------------------------- | ---------------------- |
| cloud-audit-mcp | Assess cloud CUI environment | `cloud_audit_*` tools  |
| Manual Review   | SSP and POA&M review         | Documentation analysis |

## Remediation Guide

### Requirement Statement

Monitor and control communications at external managed interfaces to the system and key internal managed interfaces within the system.
Implement subnetworks for publicly accessible system components that are physically or logically separated from internal networks.
Connect to external systems only through managed interfaces that consist of boundary protection devices arranged in accordance with an organizational security architecture.

### Supplemental Guidance

Managed interfaces include gateways, routers, firewalls, network-based malicious code analysis, virtualization systems, and encrypted tunnels implemented within a security architecture. Subnetworks that are either physically or logically separated from internal networks are referred to as demilitarized zones or DMZs. Restricting or prohibiting interfaces within organizational systems includes restricting external web traffic to designated web servers within managed interfaces, prohibiting external traffic that appears to be spoofing internal addresses, and prohibiting internal traffic that appears to be spoofing external addresses.

## Risk Assessment

| Finding                                                            | Severity | Impact                                                |
| ------------------------------------------------------------------ | -------- | ----------------------------------------------------- |
| Boundary Protection (03.13.01) Boundary Protection not implemented | High     | CUI Protection - System and Communications Protection |
| Boundary Protection (03.13.01) partially implemented (POA&M)       | Medium   | CMMC certification risk                               |

## CWE Categories

| CWE ID  | Title                                |
| ------- | ------------------------------------ |
| CWE-311 | Missing Encryption of Sensitive Data |

## References

- [NIST SP 800-171 Rev 3](https://csrc.nist.gov/pubs/sp/800/171/r3/final)
- [NIST SP 800-171A Rev 3 (Assessment)](https://csrc.nist.gov/pubs/sp/800/171/a/r3/final)
- [CMMC Model Overview](https://www.acq.osd.mil/cmmc/)
- [NIST OSCAL Content](https://github.com/usnistgov/oscal-content)

## Checklist

- [ ] SSP documents Boundary Protection (03.13.01) implementation
- [ ] Evidence of operating effectiveness collected
- [ ] POA&M addresses any gaps
- [ ] CMMC assessment objective met
- [ ] Continuous monitoring active