NIST SP 800-171
Control 3.1.21
Limit Use of Portable Storage on External Systems
CMMC-RP Certified Team
24+ Years Experience
2,500+ Clients Served
Official Requirement
Limit use of organizational portable storage devices on external information systems.
What This Means in Plain English
Company USB drives and other portable storage devices should not be plugged into systems outside your organization. This prevents malware infection and data leakage through uncontrolled external systems.
How Petronella Implements This Control
Petronella Technology Group implements this control through:
- Sophos XDR device control policies restricting USB storage usage to approved devices only
- Group Policy disabling USB mass storage on workstations by default
- Encrypted USB drives issued by IT as the only approved portable storage media
- DLP policies detecting and blocking CUI transfers to removable media
- Employee acceptable use policy prohibiting company storage devices on personal or external systems
Assessment Guidance
Assessors will verify that USB storage policies are enforced technically, test that unapproved USB devices are blocked, review DLP logs for removable media events, and check that an acceptable use policy covers portable storage on external systems.
Common Implementation Gaps
- No USB device control policies on endpoints
- Employees freely using personal USB drives
- No encryption requirement for portable storage
- No policy addressing use of company storage on external systems
- DLP not configured to monitor removable media
Cross-Framework Mapping
| Framework | Mapped Controls |
|---|---|
| NIST SP 800-53 | AC-20(2) |
| HIPAA | 164.310(d)(1) - Device and Media Controls |
Need Help Implementing 3.1.21?
Our CMMC-RP certified team can assess your current compliance posture and build a remediation plan.
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