Training & Education

Updated January 2026 How to Properly Identify, Label, and Protect Controlled Unclassified Information Physical Marking: Best Practices by Media Type Executive Summary Controlled Unclassified Information (CUI) marking is one of the most misunderstood and under-implemented components of CMMC compliance. While organizations often invest heavily in cybersecurity, they frequently overlook the physical identification and marking of CUI — creating audit risk, operational confusion, and security gaps. This CUI Marking Guide outlines the requirements, best practices, and implementation steps necessary to properly identify and label Controlled Unclassified Information (CUI) based on the real-world practices auditors and assessors expect to see. It is designed for defense contractors, manufacturers, engineers, and regulated organizations that handle sensitive government information and must meet the requirements of NIST SP 800-171, DFARS 252.204-7012, and CMMC. Inside, you’ll find straightforward guidance, real-world examples, and implementation best practices to help your organization establish consistent CUI marking standards, reduce audit risk, and strengthen both physical and cybersecurity compliance. 1. What Is CUI — And Why Marking Matters Controlled Unclassified Information (CUI) is information the U.S. Government has determined requires safeguarding or dissemination controls, but does not meet the criteria for classification. CUI exists across: Engineering drawings Manufacturing travelers Technical manuals Specifications Contracts Emails Reports CAD files Quality records Test data Export-controlled materials Why marking matters: CUI marking is foundational to compliance and security. If information isn’t clearly identified as CUI, then: Employees don’t know how to handle it Security controls can’t be applied properly Auditors can’t verify compliance Cybersecurity protections become misaligned Organizations fail CMMC assessments You cannot protect what you cannot clearly identify. 2. What Regulations Require CUI Marking? CUI marking is governed by: 32 CFR Part 2002 – CUI Program NIST SP 800-171 – Protecting CUI in Nonfederal Systems DFARS 252.204-7012 CMMC 2.0 Key Requirements: Organizations must: Identify CUI Mark it clearly Protect it physically and digitally Control dissemination Train staff on handling Marking is the trigger point that activates all downstream safeguards. 3. What Must Be Marked as CUI? CUI applies to far more than just documents. Common CUI Examples: Physical Media Printed documents Drawings Blueprints Manuals Test reports Manufacturing travelers Quality inspection records Physical Artifacts Parts or items manufactured/modified to meet military / space technical specifications Digital Media Computers Servers Hard drives USB drives CDs/DVDs Backup tapes Electronic Information Emails Shared folders Cloud storage CAD files ERP systems Facilities & Workspaces CUI work areas Engineering labs Manufacturing floors Secure rooms If it provides access to CUI, it must be treated as CUI media. 4. Core CUI Marking Requirements At minimum, CUI must be clearly labeled with: Required Markings: “CUI” banner marking CUI category (e.g., ITAR, Export Controlled, Privacy) Placement Guidelines: Top and bottom of each page (documents) Exterior of folders Visible placement on storage media Entry points of controlled areas Key Rule: Markings must be: Clear Visible Durable Consistent 5. Physical Marking: Best Practices by Media Type Documents & Paper Files Header/footer “CUI” labels File folder labels Coversheets for easy and immediate identification of CUI Best Practice: Use CUI coversheets anytime documents leave controlled spaces. Recommended Marking Solutions:CUI Document Labels, File Folder Labels, Coversheets. Computers & Digital Media Computer asset labels USB / hard drive labels Server cabinet signage Best Practice: If a system stores, processes, or transmits CUI, it must be clearly labeled. Recommended Marking Solutions:Computer & Asset Labels, USB & Digital Media Labels, Equipment Signage. Manufacturing & Engineering Environments Drawing racks Workstation signage Controlled production area signs Traveler document labeling Best Practice: Mark zones, not just documents. Recommended Marking Solutions:Workstation Signs, Production Area Signage, Document & Traveler Labels. Facilities & Rooms Restricted area signage Door labels Access-controlled entry points Best Practice: Anyone entering should instantly know CUI is present. Recommended Marking Solutions:Restricted Area Signs, Door & Entryway Labels, Facility Signage. 6. Common CUI Marking Mistakes (That Cause Audit Failures) Marking only the cover page Forgetting digital assets Unlabeled engineering workstations No signage in CUI work areas Inconsistent labeling across departments Employees unsure what qualifies as CUI Many CMMC failures happen not due to cybersecurity — but poor identification and marking. 7. A Simple 5-Step CUI Marking Program Here’s a practical roadmap companies can actually follow: Step 1 — Identify CUI Flow Map: Where CUI enters Where it’s created Where it flows Where it’s stored Step 2 — Define Marking Standards Standardize: Label designs Placement rules Handling procedures Step 3 — Deploy Physical Marking Apply: Labels Signs Coversheets Facility signage Step 4 — Train Employees Ensure staff understands: What is CUI How to recognize it How to mark it How to protect it Step 5 — Self-Audit Regularly Quarterly checks: Spot inspections Workspace audits Document reviews 8. CUI Marking Checklist (Quick Reference) Documents labeled Folders labeled Digital media labeled Computers labeled CUI rooms signed Manufacturing areas signed Transport coversheets used Staff trained 9. How CUI Supply Simplifies Compliance CUI Supply provides ready-to-deploy physical compliance solutions: CUI document labels Digital media labels Computer labels Coversheets Restricted area signage Manufacturing workstation signage Full compliance kits Our goal: Make compliance simple, fast, and audit-ready. 10. Final Takeaway CUI marking is not a paperwork exercise or a compliance formality. It is the foundation of CMMC compliance, the trigger for cybersecurity and physical security controls, and the front line of defense for protecting national security information. When CUI is clearly identified and consistently marked, organizations gain control over information flow, reduce risk exposure, simplify audits, and dramatically improve security posture across both physical and digital environments. When CUI is poorly marked or inconsistently handled, even the strongest cybersecurity investments fail to deliver real protection. Data moves without guardrails. Employees guess. Auditors flag gaps. Risk multiplies. Clear marking creates clarity. Clarity creates accountability. Accountability creates security. Organizations that treat CUI marking as a strategic priority—not just a compliance task—position themselves to pass assessments faster, reduce operational friction, and build trust with prime contractors and government partners. If it is not clearly marked, it is not protected.And if it is not protected, it becomes a business, contractual, and national security risk.