A Secure Safe Doesn't Help if the Valuables Aren't Inside It: The Case for CUI Spillage Management

CMMC has become very good at asking organizations to prove that their declared CUI environment is properly secured.

It is far less effective at proving the assumption on which the entire assessment depends:

Is the organization's CUI actually where they say (or think) it is?

The Fundamental Problem

• CMMC begins with a declared assessment scope and CUI boundary.

• 800-171 is pretty clear, scope is wherever you process, store and transmit CUI

• Assessors then evaluate whether appropriate security controls have been implemented within that environment.

• Increasingly, the industry is discussing automation as a way to make this validation faster and less expensive.

• Automated configuration validation can prove MFA is enabled, endpoints are protected, encryption is functioning, logging is occurring, and systems meet established security baselines.

• All of that is valuable.

• None of it proves that CUI isn't sitting or hasn’t spilled somewhere else.

The "Safe" Analogy

Think of the CUI enclave as a safe.

CMMC asks increasingly sophisticated questions about the safe:

• Is the door locked?

• Who has the combination?

• Is access logged?

• Is the safe physically protected?

• Does the alarm work?

• Are unauthorized people prevented from opening it?

But there is an even more fundamental question:

Did we prove the valuables are actually inside the safe?

A perfectly secured empty safe does not protect valuables sitting on someone's desk.

Where CUI Actually Escapes: Understanding CUI Spillage

Even organizations with well-designed enclaves can have CUI spillage outside their declared boundary:

• Commercial Microsoft 365 mailboxes

• SharePoint sites

• OneDrive

• Teams

• File servers

• User workstations

• PST archives

• Email attachments

• Legacy repositories

• Downloads and working copies

• 3rd party ERPs or CRMs

Finding, validating, remediating, and continuously monitoring for that CUI is what we should be thinking about as CUI spillage management. Humans, not architecture diagrams, ultimately determine where information moves and where information is stored.

The Point-in-Time Problem

Imagine a contractor successfully completes its CMMC assessment on Friday. Monday morning, an employee receives CUI in a commercial email account and saves the attachment into an unauthorized SharePoint site. Nothing about the organization's compliant enclave changed.

MFA remains enabled.

Encryption remains enabled.

Defender remains healthy.

Logging remains operational.

Every automated configuration check remains green.

But the organization's actual CUI security posture just changed.

This is the problem of CUI spillage.

Configuration Assurance ≠ CUI Assurance

These should be treated as two separate questions.

Configuration assurance asks:

Are the systems that are supposed to protect CUI configured and operating correctly?

CUI assurance asks:

Is CUI actually confined to the systems that are supposed to protect it?

Both matter. Neither answers the other.

The Missing Validation Layer

A stronger CUI assurance model should begin by challenging the organization's assertion about where CUI resides.

Declare the boundary → Independently search outside the boundary → Identify potential CUI → Validate findings → Remediate confirmed CUI → Monitor → Attest

That provides evidence supporting not only the security of the boundary but also its integrity.

Automation Should Search for the Data, Not Just the Settings

Automation absolutely has a role in modernizing CMMC. But simply automating evidence collection for technical controls risks making an existing process faster without addressing its fundamental blind spot.

The more important automation question may be:

Can we continuously determine whether sensitive government information has spilled from the environment designed to protect it?

That moves the conversation from continuous compliance monitoring toward continuous CUI assurance and spillage management.

Discovery Cannot Be a Keyword Search

Searching for the word "CUI" is not meaningful CUI validation. CUI can exist without markings. The letters "CUI" can appear in information that is not CUI.

Effective discovery therefore requires:

multiple indicators,

contextual analysis,

confidence levels,

pattern matching,

metadata,

document characteristics,

human adjudication where necessary,

and an auditable remediation workflow.

The objective is not to claim that software can perfectly determine what constitutes CUI. The objective is to systematically search for evidence that challenges the organization's assertion that CUI is confined to its authorized boundary.

Continuous Assurance

Point-in-time assessment answers:

Were you compliant when we assessed you?

Continuous CUI assurance asks:

Do we have continuing evidence that your CUI remains where you say it is?

That is a materially stronger security question.

Potential Policy Implication

As policymakers consider ways to reduce the cost and administrative burden of CMMC, the answer should not simply be replacing human assessment with automated configuration checks. There is an opportunity to rethink what we're actually trying to prove.

A future assurance model could combine:

That could potentially provide greater confidence in actual CUI protection while reducing effort spent repeatedly collecting screenshots, policies, and configuration evidence.

Closing Thought

CMMC exists because the objective is to protect Controlled Unclassified Information, not to produce compliant infrastructure. We absolutely need to know whether the safe is secure. But first, shouldn't we prove the valuables are actually inside it?

Author:

Dewayne Alford, COO

Cape Endeavors