As CMMC requirements begin appearing in defense contracts, organizations, particularly small and mid-sized businesses, face the difficult task of preparing for audits by a Certified Third-Party Assessor Organization (C3PAO). Compliance requires a serious reevaluation of how data, systems, and people interact across the enterprise. One of the most important steps before scheduling an audit is defining your Controlled Unclassified Information (CUI) boundary. Without this, your organization risks falling short before the assessment even begins.
Defining Scope
Before a CMMC Level 2 assessment, your organization must define and document the systems and services within scope. This step goes well beyond creating a simple inventory. It requires demonstrating an understanding of what CUI you have, where it is stored, how it is processed, where it flows across your environment, and who has access to it at every stage. In practice, this means creating a map of your information environment that shows how critical data moves, who touches it, and what technologies safeguard it.
Your boundary must encompass every part of the environment that interacts with CUI. This includes physical infrastructure, cloud platforms, virtual systems, identity and access management tools, and any other services that handle sensitive information. Organizations should also take time to classify assets. These include systems that store CUI directly, technologies that defend or monitor CUI systems, specialized devices such as OT or IoT equipment that cannot easily be isolated, and systems that are truly out of scope. This classification allows you to make defensible scoping decisions and gives auditors confidence that your assessment will be accurate.
It is during this stage that many organizations make mistakes. For example, contractors sometimes assume email servers are out of scope even though they transmit CUI, or they overlook a managed service provider that backs up data containing CUI. Others may ignore IoT or OT devices that cannot easily be patched or segmented. These oversights can derail an assessment quickly, which is why scoping must be both thorough and well-documented.
What is CUI?
Controlled Unclassified Information (CUI) refers to government-related data that requires safeguarding but does not meet the threshold for classification. It can include personally identifiable information, critical infrastructure data, proprietary business details, blueprints, and technical specifications. The CUI Registry defines the categories, but each organization must identify the exact types of CUI it handles and show how that information moves through its systems. A diagram of CUI flow is particularly valuable, since it highlights how information enters, where it is stored, how it is processed, and where it exits the organization.
Including Cloud and Managed Service Providers
Your CUI boundary should not be limited to systems under direct control. Many organizations rely on cloud service providers (CSPs) or managed service providers (MSPs), and these third parties are always in scope if they touch CUI or affect its security. Any CSP hosting or transmitting CUI must either hold a FedRAMP Moderate authorization or demonstrate equivalency. Similarly, any MSP with remote access, control over configurations, responsibility for backups, or other influence over the confidentiality, integrity, or availability of CUI must be included in your System Security Plan (SSP).
It is also important to understand the shared responsibility model when working with these providers. A CSP may be FedRAMP authorized, but your organization is still responsible for how user accounts, access controls, and monitoring are configured. If these responsibilities are not clearly defined in your SSP, auditors may find gaps that count against your organization.
Equally important is verifying the compliance posture of these partners. If an MSP has not passed a third-party audit, their shortcomings will count against your own assessment. Even changes in their toolsets or systems can trigger the need for reassessment, introducing both cost and delay.
Segmentation and Boundary Protections
Once your CUI boundary is established, you must also demonstrate how it is protected. This often means implementing network segmentation to isolate CUI systems from general IT environments, enforcing strict access controls, and monitoring points where CUI enters or leaves the network. Without these safeguards, a well-drawn boundary can still fail under scrutiny.
Documentation and Evidence
Defining a boundary is not enough on its own, auditors expect detailed documentation. At a minimum, this includes a System Security Plan (SSP) with diagrams of CUI flow, asset inventories, classification justifications, and network maps showing segmentation. These artifacts provide evidence that your scoping decisions are defensible and help teams maintain compliance as environments evolve.
Next Steps
Defining your CUI boundary is one of the earliest and most decisive steps in preparing for CMMC compliance. A weak or incomplete scope almost guarantees failure in front of auditors, while a thorough, well-documented one establishes the foundation for a smoother assessment.
Organizations that succeed at this step do so by taking the time to map their information flow, account for every system and provider that touches CUI, classify assets in a way that supports defensible decisions, and document how the boundary is both defined and protected. They also recognize that scoping is not a one-time exercise. Major changes in infrastructure, vendors, or toolsets require re-scoping to remain compliant.
Getting this right ensures the rest of your compliance journey is built on solid ground and positions your business to compete for defense contracts without avoidable setbacks.
How Can Netizen Help?
Founded in 2013, Netizen is an award-winning technology firm that develops and delivers innovative cybersecurity and technology solutions for government, defense, and commercial clients worldwide. Our mission is to transform complex security and compliance challenges into strategic advantages by safeguarding and optimizing digital infrastructure. One example is our “CISO-as-a-Service” offering, which enables organizations of any size to access executive-level cybersecurity expertise at a fraction of the cost of hiring internally.
Netizen operates a state-of-the-art 24x7x365 Security Operations Center (SOC) and provides a full suite of services including vulnerability assessments, penetration testing, software assurance, managed detection and response, and compliance advisory. For organizations preparing for CMMC, we currently provide CMMC pre-assessments to help contractors evaluate their readiness, map gaps against requirements, and build a remediation roadmap before undergoing a third-party audit. This proactive approach allows companies to address deficiencies early and approach certification with greater confidence.
Our organization holds ISO 27001, ISO 9001, ISO 20000-1, and CMMI Level III SVC certifications, demonstrating the maturity of our own operations. We are also a Service-Disabled Veteran-Owned Small Business (SDVOSB) recognized by the U.S. Small Business Administration, and we’ve been named to the Inc. 5000 and Vet 100 lists of the fastest-growing private companies in the nation. Netizen has been recognized as a national “Best Workplace” by Inc. Magazine and is a multi-year recipient of the U.S. Department of Labor’s HIRE Vets Platinum Medallion for veteran hiring and retention.
If your organization is preparing for CMMC compliance, Netizen can help you start with a clear picture of your current state. Our pre-assessments provide the guidance needed to plan effectively, reduce risks of failed audits, and ensure long-term alignment with DoD cybersecurity requirements.
Looking for expert guidance to secure, automate, and streamline your IT infrastructure and operations? Start the conversation today.
