CMMC Compliance Checklist

What Is CMMC Compliance?

The Department of Defense developed the Cybersecurity Maturity Model Certification to ensure that every supplier within the Defense Industrial Base maintains strong protection around sensitive defense information. Unlike previous self-attestation models, CMMC requires independent verification that an organization’s security practices are fully implemented and effective.

CMMC focuses on safeguarding CUI, or the information that, while not classified, could still cause damage to national security if stolen or exposed. With cybersecurity threats targeting defense suppliers continuing to increase, the framework provides a clear and enforceable standard for security readiness.

Why organizations must comply

Compliance is now directly tied to eligibility for DoD contracts. If an organization does not meet the required maturity level specified in a contract, it cannot bid or continue work. Beyond eligibility, regulatory compliance helps organizations:

• Prevent data breaches and business disruption
• Demonstrate credibility across the defense supply chain
• Maintain strong relationships with government stakeholders

The consequences of falling short can be significant: contract loss, legal penalties, reputational damage, and impacted revenue streams. As a result, CMMC compliance has become a top priority for contractors of all sizes.

Understanding CMMC Levels

CMMC consists of multiple maturity levels, each representing an increase in cybersecurity sophistication and documentation discipline. The goal is to ensure that controls scale with the sensitivity of the data being handled.

Level 1 — Foundational Security
Organizations establish basic cyber hygiene practices to protect Federal Contract Information (FCI), such as enforcing strong passwords and limiting physical device access. This level introduces core protections without requiring full documentation.

Level 2 — Strengthened Governance
Security practices become more defined and documented. Organizations formalize policies, track implementation, and begin adopting controls needed to protect CUI. This level serves as a stepping stone toward broader compliance.

Level 3 — Strong Cyber Hygiene
This is the most common requirement for contractors working with CUI. Teams must show consistent operational security through continuous monitoring, access control enforcement, and documented incident response procedures. Controls are based heavily on NIST SP 800-171.

Level 4 — Proactive Defense
Security becomes threat-informed and intelligence-driven. Organizations incorporate advanced tools and analytics to detect evolving attack patterns and respond quickly.

Level 5 — Optimized Security
Cybersecurity is fully integrated across processes, with automation and enterprise-wide analytics. Organizations at this level typically support the most sensitive development and mission-critical operations.

A contractor’s required maturity level depends on the information involved in a specific DoD contract. Procurement documents designate expectations, and organizations must plan cybersecurity investments accordingly. Preparing for a higher level than needed wastes resources; preparing below requirements delays contracts and triggers rework.

How to Prepare for a CMMC Assessment

Achieving compliance is not something that happens during the audit — it must be demonstrated well before an assessor arrives. Two preparation steps are especially important: documentation and internal evaluation.

Establish strong documentation and governance

• Written cybersecurity policies that outline responsibilities and required behaviors
• Standard operating procedures (SOPs) for security tasks such as access reviews, logging, and incident escalation
• System configuration baselines that show consistency and secure implementation
• Records that demonstrate security activities are executed, not theoretical

If a control is not documented or cannot be proven with evidence, auditors must treat it as non-compliant.

Conduct a comprehensive gap analysis early

• Which controls are already in place
• Where security weaknesses exist
• What must be remediated to meet the required maturity level

This step prevents surprises during the assessment and allows teams to prioritize investments around what matters most: reducing exposure of CUI.

Many contractors engage CMMC Registered Provider Organizations (RPOs) to validate readiness, assist with remediation, and ensure alignment with assessor expectations.

CMMC Compliance Checklist

Achieving CMMC compliance requires a structured, repeatable program that strengthens your organization’s defense posture over time. This checklist walks through the core domains and practices DoD contractors need to understand, prepare, and demonstrate before a third-party assessment.

1. Access Control

Strong access control is one of the cornerstones of CMMC. It ensures that only authorized personnel can view, modify, or transmit Controlled Unclassified Information (CUI).
Your organization must define, enforce, and regularly review who has access and why.
Key actions include:

• Develop and maintain role-based access policies tied to the principle of least privilege.
• Require multifactor authentication (MFA) for privileged and remote access.
• Revoke access immediately when employees change roles or leave the organization.
• Document procedures for verifying user identities and managing temporary credentials.

Access control failures are among the most common sources of breaches. Regular reviews and automated provisioning tools reduce the likelihood of human error and help auditors verify compliance more easily.

2. Asset and Configuration Management

To protect sensitive data, organizations must first know where it resides. Asset management under CMMC means maintaining visibility across every device, application, server, and virtual instance that interacts with CUI.
To comply effectively:

• Build a complete inventory of all hardware and software assets, including cloud environments.
• Implement configuration management baselines and enforce them consistently.
• Schedule regular vulnerability scans and patch management cycles.
• Document any changes to configurations and retain audit logs.

During certification, assessors will look for detailed records showing that every system handling CUI is identified, secured, and monitored for unauthorized changes.

3. Identification and Authentication

Every user and device must be uniquely identified and authenticated before accessing systems that process or store CUI. Shared accounts, weak passwords, and missing authentication layers introduce serious risk.

Organizations should use centralized identity management systems to enforce password policies, enable single sign-on (SSO) where appropriate, and use MFA. Access logs must clearly show which accounts performed specific actions, enabling accountability and forensics when necessary.

Auditors will expect to see both the technology in place and proof that authentication policies are consistently applied across the organization.

4. Incident Response

Incident response is the backbone of operational resilience. It demonstrates how prepared your organization is to contain and recover from a security event.
An effective incident response plan includes:

• Defined roles and responsibilities for each stage of incident handling.
• Documented procedures for detecting, analyzing, containing, and reporting incidents.
• Regular tabletop exercises or simulations to test readiness.
• Post-incident reviews to capture lessons learned and improve future responses.

It’s not enough to have a policy; assessors expect evidence that your teams can execute under pressure. Incident response documentation, test reports, and communication records all help demonstrate compliance.

5. Risk Management

Risk management ensures that security decisions are based on the organization’s unique threat landscape. Under CMMC, it’s not about reacting to risks after the fact; it’s about anticipating them.

Organizations should conduct risk assessments at least annually, identifying vulnerabilities, evaluating potential impacts, and documenting mitigation plans.

This includes evaluating third-party risks from subcontractors, software vendors, and cloud service providers.

A risk register should be maintained, tracking the status of each identified risk and showing how it’s addressed over time. This structured approach aligns with CMMC’s expectation for continuous improvement.

6. Security Awareness and Training

Human behavior remains a critical factor in cybersecurity incidents. CMMC requires that every employee, from executives to technical staff, understands their role in protecting sensitive data.
Effective awareness programs should:

• Include onboarding training for new hires and refresher courses at regular intervals.
• Cover topics such as phishing prevention, password security, and handling of CUI.
• Tailor content to different roles: administrators, users, and leadership.

Training builds a culture of security and ensures compliance is not limited to the IT department. It's everyone's responsibility.

7. System and Communications Protection

CMMC requires organizations to secure data in transit and at rest. Protecting communication channels ensures that sensitive data cannot be intercepted or altered.

Implement encryption protocols such as TLS for network traffic and AES-256 for stored data. Use firewalls, secure gateways, and network segmentation to limit exposure between systems.

Logs should capture communication attempts, blocked connections, and encryption key usage to demonstrate compliance. Mimecast’s email and collaboration security solutions exemplify this requirement, ensuring that messages remain tamper-proof and verifiable.

8. Maintenance and Continuous Monitoring

Ongoing maintenance verifies that your controls are implemented and working as intended. Continuous monitoring provides early warning of unauthorized access, misconfigurations, or anomalous activity.

Organizations should establish procedures for system updates, patches, and hardware replacement. Monitoring solutions should collect logs from critical systems, flag suspicious behavior, and feed alerts into a centralized dashboard or SIEM.

Evidence of this monitoring, such as automated alerts and audit logs, helps demonstrate ongoing compliance and operational maturity.

9. Recovery and Business Continuity

Even well-defended systems can experience failures or attacks. The CMMC framework emphasizes resilience or the ability to restore operations quickly while maintaining the confidentiality of CUI.

Recovery plans should define backup frequency, offsite storage, and recovery time objectives (RTOs). Test these procedures regularly to ensure they work in practice, not just on paper.

Documentation should show who is responsible for activating recovery measures, how data is restored, and how communication is handled with customers or partners during downtime.

Demonstrating a tested, functioning recovery plan is one of the strongest indicators of readiness during certification.

10. Governance, Documentation, and Audit Readiness

At its core, CMMC certification is about proof that your cybersecurity practices exist, are enforced, and are continuously maintained.

Strong governance includes:

• A centralized repository of security policies, SOPs, and control documentation.
• Records of assessments, remediation efforts, and management reviews.
• Defined escalation paths for unresolved security issues.

Before a CMMC assessment, organizations should perform a self-audit mirroring the DoD assessor’s process. This internal review highlights weak points and provides evidence of proactive data governance, a critical differentiator in competitive defense contracts.

Maintaining Compliance Post-Assessment

Continuous oversight ensures that cybersecurity controls remain effective and evolve alongside new threats, technologies, and DoD requirements.

Implement Continuous Monitoring

Once certification is achieved, organizations must sustain visibility across their security environment. Continuous monitoring validates that controls are working as intended, identifying issues before they escalate.

Regular auditing and centralized log collection are key to demonstrating accountability: capturing activity such as configuration changes, access attempts, and system alerts. When incidents occur, predefined detection and reporting processes enable teams to respond quickly, minimizing the impact on operations and compliance status.

Update Policies and Practices

Compliance frameworks evolve, and so do cyber threats. Organizations should schedule periodic reviews of their security policies, technical configurations, and documentation to reflect the latest CMMC updates or discovered vulnerabilities.

Regular employee training reinforces these updates, ensuring that every team member understands new responsibilities, reporting procedures, and the importance of data protection. Continuous learning fosters a proactive culture of security that sustains compliance between formal assessments.

Why Continuous Compliance Matters

CMMC compliance is an ongoing process that strengthens organizational resilience and builds trust across the Defense Industrial Base. A well-structured checklist provides the foundation for consistent, defensible compliance by aligning people, processes, and technology under a unified security strategy.

Organizations that maintain disciplined documentation, continuous monitoring, and regular updates are best positioned to meet evolving DoD expectations while minimizing operational risk.

Mimecast’s suite of compliance monitoring, data governance, and incident response solutions simplifies this journey. From automated threat detection to evidence preservation and reporting, Mimecast helps defense contractors maintain readiness, protect sensitive data, and demonstrate compliance with confidence.

Explore Mimecast’s compliance and cybersecurity platform to streamline your CMMC efforts and keep your organization mission-ready.