NIST SP 800-171 Rev. 3·Requirement 3.1.18·high·Component: Access Control

What this control requires

This control establishes requirements for mobile devices, including usage restrictions, configuration, and connection requirements. It mandates the authorization of mobile device connections to the system and the implementation of full-device or container-based encryption to protect the confidentiality of Controlled Unclassified Information (CUI) on mobile devices. This control supports the Mobile Device Management System capability within the Access Control (3.1) family.
— NIST SP 800-171 Rev. 3, Requirement 3.1.18

In plain English

This control establishes requirements for mobile devices, including usage restrictions, configuration, and connection requirements. 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 high. Auditors expect a named owner, a remediation SLA, and a tooling artefact that evidences continuous operation.

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 Access Control, the assessor will trace your implementation back to the catalogue reference (Requirement 3.1.18) 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.

Configuration Management

Policy-as-code. Codify the control as Service Control Policies (AWS), Azure Policy initiatives, or Organisation Policy (GCP) so the platform enforces what the document promises.

IaC. Gate Terraform / Pulumi / CloudFormation changes with Checkov / tfsec / OPA so misconfigurations never reach production.

Drift. Run a CSPM (Wiz / Prisma / Defender for Cloud / Security Command Center) over every account and route findings to a single risk register.

Operational checklist

  • Access. Document the trigger, the owner and the cadence.
  • Information. Document the trigger, the owner and the cadence.
  • Device. Document the trigger, the owner and the cadence.
  • Access Control. Document the trigger, the owner and the cadence.
  • Protection. Document the trigger, the owner and the cadence.
  • Scope: management, cui, usage restrictions, configuration, connection requirements, mobile devices, security, encryption.

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: Access Control for Mobile Devices.

Common pitfalls

  • Pilot MDM rollouts that quietly exclude executives or engineers; carving out the highest-risk users is the most common audit failure.
  • Manual cloud-console changes that never make it back to Terraform — drift accumulates until the next outage forces a reconciliation.

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 securitydata protectionendpoint protectionconfiguration managementencryption at rest