Prohibit the use of portable storage devices when such devices have no identifiable owner
📖 What This Means
This practice requires organizations to ensure that portable storage devices, such as USB drives or external hard drives, are only used if they have a clear, identifiable owner. This means that any device without an assigned owner or proper labeling should not be used to store or transfer Controlled Unclassified Information (CUI). The goal is to prevent unauthorized access, loss, or misuse of sensitive data. For example, if an employee finds a USB drive in the office parking lot, it should not be plugged into any company computer without first verifying its owner and contents. This control helps maintain accountability and reduces the risk of data breaches.
🎯 Why It Matters
Unattributed portable storage devices pose a significant security risk because they can introduce malware, lead to data leaks, or be used for unauthorized data exfiltration. For instance, the 2008 U.S. military breach involving malware-laden USB drives highlighted the dangers of unregulated portable media. Such incidents can result in costly fines, reputational damage, and loss of sensitive information. From the DoD/CMMC perspective, this control ensures that only authorized personnel can use portable devices, reducing the attack surface and ensuring accountability. Failure to enforce this practice can lead to non-compliance with CMMC requirements and jeopardize contracts.
✅ How to Implement
- 1. Disable USB ports on virtual machines (VMs) hosting CUI in AWS, Azure, or GCP.
- 2. Use cloud-native endpoint protection tools (e.g., Microsoft Defender for Endpoint) to detect and block unauthorized portable devices.
- 3. Implement Conditional Access Policies in Azure AD to restrict device usage.
- 4. Log and monitor USB device activity using cloud-based SIEM tools like Splunk or Azure Sentinel.
- 5. Train employees on cloud-specific policies for portable device usage.
📋 Evidence Examples
Portable Device Usage Policy
USB Port Configuration Screenshot
Authorized Device Registry
Training Attendance Record
Audit Logs
📝 SSP Guidance
Use this guidance when writing the System Security Plan (SSP) narrative for this control.
How to Write the SSP Narrative
For MP.L2-3.8.8 ("Prohibit the use of portable storage devices when such devices have no identifiable owner"), your SSP narrative should specifically describe: (1) the tools and technologies you use to implement this control, (2) the configuration or process that enforces it, (3) who is responsible for maintaining it, and (4) what evidence proves it's working. Describe how CUI on media is protected throughout its lifecycle, including encryption, access controls, marking, transport procedures, sanitization methods, and accountability tracking. Be specific -- name your actual products, settings, and responsible personnel.
Example SSP Narratives
"MP.L2-3.8.8 is implemented using cloud-native controls. [Organization] uses [specific cloud service/feature] to prohibit the use of portable storage devices when such devices have no identifia.... The configuration is managed through [Azure Policy/AWS Config/Terraform] and monitored via [SIEM tool]. Responsible party: [IT Security Manager]. Evidence: [specific artifact, e.g., 'Azure AD Conditional Access policy screenshot, CloudTrail logs']."
"MP.L2-3.8.8 is implemented through on-premise infrastructure controls. [Organization] uses [Active Directory/Group Policy/specific tool] to prohibit the use of portable storage devices when such devices have no identifia.... Configuration is documented in [location] and audited [frequency]. Responsible party: [System Administrator]. Evidence: [specific artifact, e.g., 'Group Policy export, Windows Event logs']."
"MP.L2-3.8.8 is implemented across both cloud and on-premise environments. [Organization] uses [Azure AD Connect/hybrid tool] to ensure consistent enforcement. Cloud resources are managed via [cloud tool] and on-premise systems via [on-prem tool]. Both environments report to [centralized SIEM]. Responsible party: [IT Director]. Evidence: [artifacts from both environments]."
System Boundary Considerations
- • Identify all removable media types within the CUI boundary
- • Document media storage locations (on-site, off-site)
- • Specify media sanitization and destruction methods
- • Ensure this control covers all systems within your defined CUI boundary where prohibit the use of portable storage devices when such devices have no identifiable owner applies
- • Document any systems where this control is not applicable and explain why
Key Documentation to Reference in SSP
- 📄 Media Protection Policy
- 📄 Media inventory database
- 📄 Certificates of destruction
- 📄 Transport chain-of-custody records
- 📄 Evidence artifacts specific to MP.L2-3.8.8
- 📄 POA&M entry if control is not fully implemented
What the Assessor Looks For
The assessor will check for CUI markings on media, verify encryption is enabled, review the media inventory for completeness, and examine destruction certificates.
💬 Self-Assessment Questions
Use these questions to assess your compliance. Each "NO" answer provides specific remediation guidance.
Question 1: Do you have a documented policy prohibiting the use of unowned portable storage devices?
Question 2: Are USB ports disabled on all systems handling CUI?
Question 3: Do you maintain a registry of authorized portable devices and their owners?
Question 4: Have employees been trained on portable device policies?
Question 5: Are USB device activities logged and monitored?
⚠️ Common Mistakes (What Auditors Flag)
1. USB ports not disabled on all systems.
2. No registry of authorized devices.
3. Employees using unapproved devices.
4. Inadequate logging of USB activity.
5. Policy not updated to reflect current practices.
📚 Parent Policy
This practice is governed by the Media Protection Policy