NIST SP 800-171 Rev. 3·Requirement 3.13.1·critical·Component: Situational Awareness

What this control requires

This control requires monitoring and controlling communications at external and key internal interfaces to the system, implementing subnetworks (DMZs) for publicly accessible components, and connecting to external systems only through managed interfaces with boundary protection devices. These measures help secure communication paths and prevent unauthorized access or spoofing. This control supports the Boundary Protection capability within the Situational Awareness (3.13) family.
— NIST SP 800-171 Rev. 3, Requirement 3.13.1

In plain English

This control requires monitoring and controlling communications at external and key internal interfaces to the system, implementing subnetworks (DMZs) for publicly accessible components, and connecting to external systems only through managed interfaces with boundary protection devices. In practice, this means you can prove you access management-level controls on a defined cadence.

Why it matters

DoD contractors and their subcontractors must implement all 100 SP 800-171 requirements to keep CUI handling contracts. Gaps are scored against the SPRS scoring methodology; below a 110-point starting score, each unmet requirement deducts points and a below-threshold score can disqualify a bid.

This control is rated critical in the source catalogue. Treat gaps here as production incidents in the risk register, not housekeeping.

What an auditor looks for

A C3PAO conducting a CMMC Level 2 assessment uses NIST SP 800-171A objectives. They expect a System Security Plan (SSP), Plan of Action & Milestones (POA&M) for any gaps, and objective evidence (configurations, ticket records, training records) for every requirement.

Within Situational Awareness, the assessor will trace your implementation back to the catalogue reference (Requirement 3.13.1) and look for objective evidence on the latest two assessment cycles.

How to implement

Endpoint Protection

MDM. Make MDM enrollment a hard gate for device access (Intune compliance + Conditional Access, or Jamf + Okta device trust). Unmanaged devices simply don't get a session token.

EDR. Deploy CrowdStrike / SentinelOne / Defender for Endpoint to every server and laptop; alert on any host that stops sending telemetry for >24h.

Operational checklist

  • Access. Document the trigger, the owner and the cadence.
  • Publicly. Document the trigger, the owner and the cadence.
  • Protection. Document the trigger, the owner and the cadence.
  • System. Document the trigger, the owner and the cadence.
  • Security. Document the trigger, the owner and the cadence.
  • Scope: management, external systems, security, protection.

Evidence to collect

  • User Device Scan. MDM compliance state per user device (Intune / Jamf / Workspace ONE).
  • Infra Scan. Continuous infrastructure-posture telemetry — AWS Config, Azure Policy compliance, GCP Organisation Policy, Wiz / Prisma findings.

Endpoint compliance telemetry (Intune, Jamf) proves managed coverage. Focus: Boundary Protection.

Common pitfalls

  • Pilot MDM rollouts that quietly exclude executives or engineers; carving out the highest-risk users is the most common audit failure.

How it maps to other frameworks

Computed from shared tags, control component and key-operation subjects — handy when you are reconciling controls across an audit.

Related controls in NIST SP 800-171 Rev. 3

References

Topics: endpoint securitylogging monitoringendpoint protectioncontinuous monitoringkey management