NIST 800-171 Control 3.8.4: Media Marking
Controlled Unclassified Information (CUI) requires clear marking on physical and digital media to prevent unauthorized access and distribution. Control 3.8.4 mandates that organizations label media with appropriate CUI markings and communicate distribution restrictions to users. This foundational practice reduces accidental disclosure and ensures information handlers understand data sensitivity.
What this means
Media marking requires you to apply visible, standardized CUI designations to all storage media (USB drives, hard drives, optical discs, printed documents) that contain protected information. These markings must identify the CUI category, handling restrictions, and authorized recipients. Distribution limitations—such as 'internal use only' or 'authorized personnel only'—must be clearly communicated and enforced through policy and training.
How to comply
- 1.Establish a media marking standard that aligns with CUI categories (technical data, financial records, etc.) and your organization's classification scheme
- 2.Physically label all removable media (drives, tapes, DVDs) with CUI markings before use or distribution
- 3.Apply header and footer markings to sensitive digital documents and emails containing CUI
- 4.Document distribution limitations on media labels and in data handling policies
- 5.Train all staff on recognizing CUI markings and adhering to stated distribution restrictions
- 6.Audit media inventory quarterly to ensure markings remain visible, intact, and up-to-date
- 7.Implement automated labeling tools for digital files to reduce manual marking errors
Evidence auditors look for
- Marked USB drives with CUI designation, handling category, and point-of-contact for questions
- Email templates with auto-populated CUI headers and footer warnings on sensitive message threads
- Physical media log documenting all marked drives, their contents, recipients, and distribution dates
- Policy document specifying media marking requirements, authorized label formats, and distribution rules
- Training records showing staff completion of CUI marking and handling awareness modules
- Quarterly media audit report confirming all CUI-containing devices are properly labeled
- Inventory spreadsheet tracking media serial numbers, contents, classification level, and current location
Frequently asked questions
When will FAQs be available?
The FAQ for this control is currently being prepared.
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