The journey to CMMC Level 3 represents the highest level of cybersecurity maturity under the CMMC framework. Unlike Levels 1 and 2, which focus on FCI and CUI, respectively, Level 3 targets Advanced Persistent Threats (APTs). That means more extensive security, defined in NIST Special Publication 800-172.

For organizations that support critical programs or handle high-value assets for the Department of Defense, achieving Level 3 is imperative. But what does it take to implement the enhanced controls from NIST SP 800-172, and how do they fit into the broader CMMC ecosystem? This article explores that challenge and provides a practical roadmap for organizations preparing to meet it.

Understanding the Role of NIST SP 800-172 in CMMC Level 3

NIST SP 800-171 outlines 110 security requirements that form the backbone of CMMC Level 2. But Level 3 raises the stakes. According to the CMMC Assessment Guide for Level 3, a selected subset of NIST SP 800-172’s 35 enhanced requirements is applied on top of the 800-171 baseline.

These enhanced controls are intended to defend against nation-state-level adversaries. They’re not just about better passwords or stricter firewall rules; they demand architectural decisions, proactive threat response capabilities, and the implementation of cyber-resilient operations.

Not all of 800-172 is required for CMMC Level 3. The DoD has curated a targeted set of controls that align with specific threat vectors relevant to critical missions. Understanding which controls are in scope is the first major step.

Mapping Your 800-172 Readiness

Your readiness assessment should begin with a clear mapping exercise. Each enhanced control from the CMMC Level 3 guide is linked to a requirement in NIST SP 800-172, and the language often carries over verbatim.

A practical tool is a matrix that includes:

• The CMMC control identifier
• The corresponding 800-172 citation
• Implementation status (implemented, in progress, not started)
• Responsible team or owner
• Supporting documentation and evidence

This mapping exercise doesn’t just prepare you for assessment; it reveals where your security architecture may still be designed for Level 2 threats, not Level 3 adversaries.

Three Areas of Strategic Focus

NIST SP 800-172 is organized around three high-level defensive strategies. Understanding and executing on these strategies is essential to practical implementation.

• Penetration-Resistant Architecture: You can no longer assume perimeter defense is enough. Your internal systems must be hardened and compartmentalized. This means secure administrative environments, isolated CUI enclaves, and strong boundary protections that limit lateral movement within your network. Think of it as building interior walls, not just stronger locks on the front door.
• Damage-Limiting Operations: The assumption is not if an adversary gets in, but when. Damage-limiting strategies include limiting privilege escalation, implementing behavior-based detection, and isolating critical functions. Technologies like deception tools, privileged access workstations (PAWs), and strict session controls become essential.
• Cyber Resiliency: This is about sustaining operations and recovering quickly. Expect to implement redundant systems, out-of-band management, and resilient communications. But more importantly, it means adopting a threat-informed mindset, continuously reassessing your defensive posture against evolving adversary tactics.

Control Implementation 

Several controls stand out as both technically complex and strategically important:

• RA.L3-3.11.2e – Threat Hunting: This is not your standard log review. This requires organizations to proactively hunt for indicators of compromise based on known and emerging threat intelligence. Implementing this means investing in skilled analysts and threat intelligence feeds, and integrating hunt activities with your SIEM or XDR platform.
• CA.L3-3.12.1e – Penetration Testing: This control requires you to assess your defenses from an adversary’s perspective. Penetration testing must go beyond compliance checklists to simulate real-world attack paths. Results must feed back into your remediation plans and system design.
• IA.L3-3.5.1e – Bidirectional Authentication: Mutual authentication verifies both parties in a communication. This goes beyond simple MFA. Examples include TLS client authentication, certificate pinning, or mutual SSH key validation. It is often most applicable in system-to-system or service-to-service communications.
• SI.L3-3.14.6e – Threat-Guided Intrusion Detection: Signature-based tools are no longer sufficient. This control requires the use of behavioral analysis and threat intelligence to guide detection. Implementing this might involve leveraging MITRE ATT&CK mappings and customizing detection rules based on adversary TTPs.

Preparing for the DCMA DIBCAC Assessment

CMMC Level 3 assessments are performed exclusively by the Defense Industrial Base Cybersecurity Assessment Center (DIBCAC). That means there is no self-attestation and no room for assumptions.

Organizations seeking Level 3 certification must first achieve Final Level 2 (C3PAO) status. Only then can a Level 3 assessment be requested. Before that assessment takes place, preparation is critical.

Recommendations include:

• Conduct a mock Level 3 assessment using the official assessment guide.
• Ensure that all POA&Ms from Level 2 are closed out. No open items are allowed at Level 3.
• Prepare documentation that justifies your implementation approach, including system design diagrams, risk assessments, threat models, and control rationales.
• Train your staff. DCMA will interview both technical and operational personnel during the assessment.

Reach and Manager Level 3 Compliance with Continuum GRC

If your organization supports DoD critical programs or handles high-value CUI, you may already be in scope for Level 3. Now is the time to assess, design, and act. Because adversaries aren’t waiting for you to get certified.

We provide risk management and compliance support for every major regulation and compliance framework on the market, including:

• FedRAMP
• StateRAMP
• GDPR
• NIST 800-53
• FARS NIST 800-171
• CMMC
• SOC 1, SOC 2
• HIPAA
• PCI DSS 4.0
• IRS 1075
• COSO SOX
• ISO 27000 Series
• ISO 9000 Series
  
• ISO Assessment and Audit Standards

And more. We are the only FedRAMP and GovRAMP-authorized compliance and risk management solution worldwide.

Continuum GRC is a proactive cybersecurity® platform and the only worldwide FedRAMP and GoveRAMP-authorized cybersecurity audit platform. Call 1-888-896-6207 to discuss your organization’s cybersecurity needs and learn how we can help protect your systems and ensure compliance.