NIST SP 800-171 Control 3.8.8: Shared Media Prohibition
Control 3.8.8 requires organizations to prohibit the use of portable storage devices that lack identifiable ownership. This critical control prevents data exfiltration and unauthorized access by ensuring all removable media can be traced to a specific user or system. For SMBs handling controlled unclassified information (CUI), implementing shared media prohibition is essential to meet NIST 800-171 compliance requirements.
What this means
Shared media prohibition means banning the use of any portable storage device—such as USB drives, external hard drives, or memory cards—that cannot be definitively linked to an individual owner or authorized system. The control eliminates the risk of orphaned devices being used to transfer sensitive data without accountability. Only storage media with clear ownership documentation and user accountability may be used within your organization.
How to comply
- 1.Establish a written policy prohibiting use of unowned portable storage devices across all systems and locations
- 2.Create a centralized inventory of all approved portable media devices with documented owner names and asset tags
- 3.Implement technical controls (e.g., USB port disabling, Mobile Device Management) to enforce the prohibition at the hardware or OS level
- 4.Require employees to register any portable storage device before use, documenting the owner and intended purpose
- 5.Conduct regular audits to identify and remove non-compliant unowned devices from organizational networks
- 6.Provide alternative secure file-sharing solutions (encrypted cloud storage, approved file transfer tools) to reduce reliance on portable media
- 7.Train all staff on the shared media policy and consequences of non-compliance
- 8.Document all exceptions with justification and compensating controls if approved portable media is required
Evidence auditors look for
- Documented portable storage device prohibition policy signed by management
- Asset inventory log listing all approved portable media with owner names and serial numbers
- Screenshots or reports from endpoint protection software showing USB restriction enforcement
- Device registration forms completed for each approved portable storage device
- Audit logs from security scans detecting and flagging unowned devices
- Approved file-sharing platform usage reports as evidence of secure alternatives in use
- Employee training records and acknowledgment forms confirming awareness of shared media prohibition
- Exception approval documentation with risk assessments for any permitted unowned media use
Frequently asked questions
When will FAQs be available?
The FAQ for this control is currently being prepared.
GRCWatch automates the tracking and enforcement of device ownership requirements by maintaining a centralized portable media inventory, alerting you when unregistered devices are detected, and generating audit-ready compliance reports—eliminating manual spreadsheet management for NIST 800-171 3.8.8.
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