M365: Cloud-Based CUI Under NIST 800-171 Compliance
Secure by Default. Compliant by Design.
A practical, scalable CUI solution built on Microsoft 365 and managed by Prestwood IT.
At Prestwood IT, we implement Controlled Unclassified Information (CUI) compliance the smart way—starting with Microsoft 365 Business Premium and our proven Managed IT stack. You get device-level security, patch management, and endpoint protection with Bitdefender, all managed under one plan. Then, we add only what’s required for your industry or audit—like disk encryption monitoring, S/MIME email protection, and centralized password oversight. The result? A future-ready solution that’s compliant, cost-effective, and tailored to how your business actually works.
The Prestwood CUI Strategy
We implement our Full Security Model—Managed IT + Managed M365 + Conditional Services—and then adjust additions (like S/MIME, NordPass, disk encryption, backup) only if your auditor specifies them or known otherwise. We deploy Classic Outlook with purchased S/MIME certificates when secure email is explicitly required by contract or auditor.
Optional Add-Ons (Auditor-Driven):
• N-Central Disk Encryption Management: Added only when centralized encryption proof is requested.
• NordPass for Business: Activated if controlled password management is mandated.
• N-Able File-Based Backup: Deployed when data restoration policy requires it.
CUI Compliance in Microsoft 365
Minimally Required Setup for Handling CUI
Designed to meet the NIST 800-171 controls for Controlled Unclassified Information
This baseline configuration enables your organization to securely handle CUI using Microsoft 365 and aligned tools. It is tailored to meet the minimum security expectations under NIST 800-171 and is compatible with CMMC Level 2 requirements.
🔧 Core Solution Components
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Microsoft 365 Business Premium
Full compliance support starts with Business Premium, which includes:-
Azure AD (Entra ID) for identity management
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Intune for device compliance and conditional access
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Defender for Business for endpoint security
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BitLocker support (if managed properly)
💡 If your compliance auditor requires elevated Microsoft licensing, we can also implement this using Microsoft 365 E3 or E5.
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Managed IT Plan (Prestwood IT + N-Able N-Central)
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Remote Monitoring and Management (RMM)
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Antivirus + Endpoint Protection
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Patch Management for Windows and supported 3rd-party apps
💡 This plan ensures operational security controls like AV, patching, system health monitoring, and alerting — critical for meeting CUI’s ongoing maintenance expectations.
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N-Central Disk Encryption Service (Optional, Based on Compliance)
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Monitor, manage, and audit BitLocker on Windows devices
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Centralized encryption reporting for compliance tracking
⚠️ Required only if your CUI handling policy or auditor calls for centralized at-rest encryption visibility and auditing.
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NordPass for Business (Optional, Based on Compliance)
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Secure password storage
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Role-based access and audit logging
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Supports individual and shared credentials
⚠️ Required only if your policy calls for centralized password control or your auditor flags password management risk.
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📋 Technology Requirements Table for CUI in Microsoft 365
| Component | Purpose | Required for CUI? | Notes |
|---|---|---|---|
| Microsoft 365 Business Premium | Identity, device management, conditional access, endpoint protection | ✅ Yes | Use E3 or E5 only if required by your compliance auditor |
| Entra ID + Intune | Device compliance, conditional access, remote wipe, least privilege enforcement | ✅ Yes | Included with Business Premium; required for device-level Zero Trust |
| BitLocker | Encrypts stored CUI data at rest on endpoints | ✅ Yes | Required by NIST 800-171 control 3.13.16 (At-Rest Encryption) |
| Disk Encryption Audit (N-Central) | Monitors and verifies BitLocker is active across devices | ⚠️ Optional | Use if your policy or auditor requires centralized encryption proof |
| S/MIME Email Encryption | Encrypts and signs emails to protect CUI in transit | ✅ Yes | Requires Classic Outlook app; not supported in New Outlook, OWA, or mobile |
| N-Central AV + Patch Management | Monitors endpoints, installs updates, enforces health baselines | ✅ Yes | Part of our Managed IT Plan; aligns with system maintenance controls |
| NordPass for Business | Centralized password management with audit trails and access control | ⚠️ Optional | Use if your compliance scope includes centralized credential oversight |
📋 Choosing the Right M365 License for CUI Compliance
This table compares the three Microsoft 365 plans we offer for CUI compliance. Most clients choose Business Premium. Upgrade to E3 for advanced compliance tools and scalability. Upgrade to E5 only if your auditor requires automated data protection, audit logging, or advanced classification.
| Feature / Compliance Area | Business Premium | M365 E3 | M365 E5 * |
|---|---|---|---|
| Included Auto-Upgraded Windows License | Windows Business | Windows Enterprise | Windows Enterprise |
| Entra ID (Azure AD) | ✅ Included (P1) | ✅ Included (P1) | ✅ Included (P2) |
| Intune (Endpoint Compliance) | ✅ Included | ✅ Included | ✅ Included (via EMS E5) |
| Conditional Access | ✅ Included | ||
| Endpoint Security | ✅ Included in Managed IT Plan | ||
| BitLocker Storage via Intune | ✅ Supported | ||
| At Rest Management & Audit | ⚠️ Not generally required, available with addon N-Central Compliance | ||
| S/MIME Email Encryption | ✅ Yes (Classic Outlook only) | ||
| Data Loss Prevention (DLP) File-Based Backup | ⚠️ Not generally required, available with addon N-Central Backup | ||
| DLP Labels | ❌ Not included ** | ✅ Included | ✅ Full DLP + Endpoint DLP |
| Auto-Labeling & Info Protection (Purview) | ❌ Not included ** | ✅ AIP Plan 1 | ✅ Included |
| Insider Risk / Audit Logging | ❌ Not included ** | ❌ Basic logging only | ✅ Advanced visibility + alerts |
| OneDrive Storage | 1 TB/user | 5 TB+ (with 5+ users) | 5 TB+ |
| User Cap | 300 | Unlimited | Unlimited |
* M365 E3 includes all the security and device management of Business Premium, with added enterprise tools like enhanced SharePoint, AIP, and larger storage limits. E5 adds advanced protection, threat analytics, and audit capabilities that may be required depending on your compliance auditor.
** Sometimes required after an audit.
🔍 Choosing Between Premium, E3, and E5 for CUI Compliance
Use this step-by-step guide to help determine the right Microsoft 365 license for your organization under NIST 800-171 and CMMC 2.0 requirements.
🔹 Are you required to handle CUI (Controlled Unclassified Information)?
✅ Yes — Business Premium meets all baseline CUI compliance needs, including Intune, device compliance, and secure collaboration tools.
Continue below.
🔹 Do you need more storage, large-scale user support, or enterprise-grade SharePoint/compliance features?
➡️ If yes, upgrade to E3. It includes everything in Business Premium, with no user cap and more enterprise tools — but no added security complexity.
🔹 Has an auditor requested:
- Auto-labeling or Microsoft Purview Information Protection?
- Advanced DLP across Teams, devices, and files?
- Detailed audit logs or Insider Risk Management?
✅ If yes, E5 is required to meet these advanced compliance needs. We may also explore Microsoft Purview add-ons or GCC High depending on contract scope.
🔹 Are you pursuing CMMC Level 3 or handling ITAR, FCI, or high-security government workloads?
⚠️ If yes, contact us for guidance. You may need Microsoft 365 GCC E3 or E5, which we can provision for qualified clients.
❌ If your contracts specifically require GCC High, those licenses can only be purchased through select government-authorized resellers — not through Prestwood IT. We’ll help you determine what’s required and connect you with trusted partners if needed.
✅ Otherwise: Stick with Business Premium. It provides full CUI compliance when paired with strong security practices — which we deliver as part of our Managed IT and Managed M365 plans on our Full Security Model.
Summary: Most small and midsize businesses handling CUI can confidently use Microsoft 365 Business Premium with our layered compliance stack. Only upgrade to E3 or E5 if contractually required, flagged in an audit, or you need advanced labeling, DLP, or insider risk features.
Solid Security Now and Future-Ready
Baseline today. Compliance when you need it.
Our M365 Company-in-the-Cloud core setup prepares your business for the AI-driven future and its evolving security demands. When you’re ready, layer in advanced services like sensitivity labels, DLP policies, encryption tuning, and device compliance — plus full HIPAA, CUI, NIST, or SOC 2 readiness. All billed hourly, only as needed.
