NIST 800-171 Control 3.1.3: CUI Flow Enforcement
Control 3.1.3 requires you to enforce approved data flows for Controlled Unclassified Information (CUI) across your systems and networks. This foundational control prevents unauthorized movement of sensitive data and ensures only authorized users and systems can access CUI based on their clearance and need-to-know. Non-compliance exposes your organization to data breaches, loss of government contracts, and regulatory penalties.
What this means
CUI flow enforcement means establishing and implementing rules that govern how sensitive government information moves through your infrastructure. You must define approved data paths, restrict transfers between systems, and prevent CUI from flowing to unauthorized locations or users. This includes controlling data at rest, in transit, and during processing—ensuring every movement aligns with documented authorization policies.
How to comply
- 1.Document approved CUI data flows and authorization rules in your information security policy
- 2.Implement technical controls (firewalls, access controls, encryption) that enforce documented flow policies
- 3.Define data classification labels and apply them consistently across systems to track CUI movement
- 4.Establish audit logging for all CUI transfers to create an audit trail of data movements
- 5.Review and test data flow controls quarterly to ensure they remain effective and aligned with authorizations
- 6.Train staff on approved data handling procedures and consequences of unauthorized CUI transfers
- 7.Maintain a current inventory of systems and networks that can receive or process CUI
Evidence auditors look for
- CUI data flow diagrams showing authorized paths between systems and users
- Firewall rules, ACLs, and network policies enforcing CUI movement restrictions
- Data classification and labeling standards applied to CUI throughout your environment
- System audit logs showing CUI access, transfer, and processing events with timestamps
- Quarterly control testing reports validating that data flows comply with authorizations
- Staff training records documenting CUI handling and flow enforcement procedures
- Change management logs for updates to data flow policies or technical controls
Frequently asked questions
When will FAQs be available?
The FAQ for this control is currently being prepared.
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