Portable Storage Use
Limit use of portable storage devices on external systems.
What an assessor scores, the objectives
AC.L2-3.1.21 is met only when every one of these 3 objectives, from NIST SP 800-171A, is satisfied. A single missed objective makes the whole requirement not met.
- a.the use of portable storage devices containing CUI on external systems is identified and documented
- b.limits on the use of portable storage devices containing CUI on external systems are defined
- c.the use of portable storage devices containing CUI on external systems is limited as defined
How a C3PAO checks it
NIST SP 800-171A defines three assessment methods. For AC.L2-3.1.21, an assessor uses these:
Access control policy; procedures addressing the use of external systems; system security plan; system configuration settings and associated documentation; system connection or processing agreements; account management documents; other relevant documents or records
Personnel with responsibilities for restricting or prohibiting use of organization-controlled storage devices on external systems; sy stem or network administrators; personnel with information security responsibilities
Mechanisms implementing restrictions on use of portable storage devices
What it means, in context
Limits on the use of organization -controlled portable storage devices in external systems include complete prohibition of the use of such devices or restrictions on how the devices may be used and under what conditions the devices may be used. Note that while “external” typically refers to outside of the organization’s direct supervision and authority that is not always the case. Regarding the protection of CUI across an organization, the organization may have systems that process CUI and others that do not. Among the systems that process CUI there are likely access restrictions for CUI that apply between systems . Therefore, from the perspective of a given system, other systems within the organization may be considered “external" to that system.
A portable storage device is a system component that can be inserted or attached and easily removed from a system. It is used to store data or information. Examples of portable storage devices include: • compact/digital video disks (CDs/DVDs); • Universal Serial Bus (USB) drives; • external hard disk drives; • flash memory cards/drives; and • floppy disks. This requirement can be implemented in two ways: • identifying the portable storage device usage restrictions, identifying portable storage devices that may be used on external systems, identifying associated external systems on which a portable storage device may be used, and administratively (through the use of a written policy) limiting the usage of the devices to those systems; or • configuring devices to work only when connected to a system to which the portable storage device can authenticate, limiting the devices ’ use on external systems to those that the OSA has the ability to manage. Example Your organization, which stores and processes CUI, has a written portable device usage restriction policy. It states that users can only use external storage devices such as thumb dives or external hard disks that belong to the company. When needed for a specific business function, a user checks the device out from IT and returns it to IT when no longer needed [a,b]. Potential Assessment Considerations • Are the portable storage devices authorized for external use identified and documented [a]? • Are the circumstances defined in which portable storage devices containing CUI may be used on external systems (e.g., with management approval) [b]? • Are limitations stipulated for the use of portable storage devices containing CUI on external systems (e.g., authorized personnel only, encrypted drives required) [b]?
What passing evidence looks like
The portable storage rule for YOUR devices used on external systems, and the technical or procedural limit that enforces it.
Common ways contractors fail AC.L2-3.1.21
- !This is about your organization's portable storage plugged into systems outside your boundary (a thumb drive to the prime's machine). Distinct from MP.L2-3.8.7, which governs removable media inside your systems.
The step by step walkthrough for Microsoft 365 GCC High, Google Workspace, and on premises setups, plus the exact evidence to capture, lives inside the Level 2 Accelerator.
Prove AC.L2-3.1.21, and the other 109
The Level 2 Accelerator walks all 110 requirements with you, generates your SSP, POA&M, and Audit Room from real evidence, includes the full Level 1 platform, and puts a credentialed officer alongside you for 180 days. Filed in 180 days, or we work free until you are.
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AC.L2-3.1.21 questions, answered
How many points is CMMC requirement AC.L2-3.1.21 worth?+
AC.L2-3.1.21 is worth 1 point in the CMMC Level 2 score under 32 CFR 170.24. If it is not met, you lose 1 from your total of 110.
Can AC.L2-3.1.21 be placed on a POA&M?+
Yes. A gap on AC.L2-3.1.21 can be deferred to a Plan of Action and Milestones, provided your overall score is 88 or better and the item closes within 180 days.
What family does AC.L2-3.1.21 belong to?+
AC.L2-3.1.21 is in the Access Control (AC) family, one of the 14 families of NIST SP 800-171 that make up CMMC Level 2.
- NIST SP 800-171 Rev. 2 3.1.21