Top 15 Most Common CMMC Compliance Mistakes Series #1
This article is part of our expert-led series: The Top 15 Most Common CMMC Compliance Mistakes (and How to Solve Them). Throughout this series, we're dissecting the frequent errors, misunderstandings, and misconceptions organizations encounter on their path to CMMC certification, drawing insights from seasoned CCPs, CISOs, and CCAs.
Today’s focus: The critical importance of accurately scoping your CMMC environment, ensuring all relevant assets and data flows are properly identified and documented.
What You’ll Learn
- How to identify and categorize assets within your CMMC scope
- The significance of mapping information flows, particularly for Controlled Unclassified Information (CUI)
- Strategies to avoid over-scoping or under-scoping your environment
- Best practices for maintaining an accurate and up-to-date scope
Why Scoping Is So Foundational
CMMC assessments don’t look at your entire company, they look at the portion of your business environment that stores, processes, or transmits Controlled Unclassified Information (CUI) and Federal Contract Information (FCI). This subset is your Assessment Scope, and it defines everything from documentation requirements to technical control implementation.
Improper scoping can result in:
- Exposing sensitive assets that were incorrectly excluded
- Inflated project costs and resource strain from over-scoping
- Gaps in policy, procedure, or control coverage
- Failed assessments due to inadequate or irrelevant system boundaries
Where Most Businesses Get It Wrong
Most companies make two key scoping errors:
- They don’t trace CUI and FCI flow across business processes.
CUI isn’t just stored, it’s emailed, printed, shared over meetings, entered into databases, and discussed with contractors. A failure to map this entire lifecycle leads to blind spots. - They don’t align their scoping decisions with NIST 800-171 and CMMC Assessment Process (CAP) guidance.
CMMC requires documented justifications for scoping decisions, and these need to align with definitions in the CAP and guidance from the DoD. Many companies simply make assumptions.
How to Properly Scope Your Environment
To define the right scope for your CMMC assessment, follow this process:
- Identify all systems that store, process, or transmit CUI/FCI.
Include SaaS applications, on-prem assets, employee endpoints, third-party integrations, and backups. - Map the flow of CUI/FCI through business processes.
Create visual diagrams or flowcharts showing where data enters, moves, is stored, and exits. - Segment the environment.
Use network segmentation or enclaves to isolate CUI environments from corporate or guest systems. This minimizes scope and simplifies compliance. - Assign roles and responsibilities.
Every system, user, and boundary needs an owner who understands their role in protecting CUI. - Document everything.
Include clear diagrams, boundary definitions, control applicability, and justification for exclusions in your SSP.
The Link Between Scoping and Cost
One of the most practical reasons for proper scoping is cost containment. CMMC compliance is significantly more expensive when scope is too broad, especially when compliance controls are applied to systems or personnel who have no need for CUI access.
A precise scope reduces:
- Total system hardening efforts
- Licensing and monitoring expenses
- Policy development workload
- Assessment duration and complexity
In Summary: Compliance Requirements Reach Further Than You May Think
Accurate scoping is essential for effective CMMC compliance. By thoroughly identifying and categorizing assets and mapping information flows, organizations can apply appropriate security controls, avoid unnecessary compliance efforts, and ensure all vulnerabilities are addressed.
Key Takeaways
- Proper scoping ensures all assets interacting with CUI are identified and secured.
- Data flow diagrams are vital tools for visualizing CUI movement within the organization.
- Regular reviews and updates to the scope maintain compliance as systems evolve.
Up Next In Our Top 15 Most Common CMMC Mistakes Series:
As we conclude this series, we’ll wrap up with a summary of all Top 15 CMMC Compliance Mistakes we see Businesses Make and a step-by-step action plan for building a defensible, audit-ready CMMC program.