3.1.21Limit portable storage on outside systems

USB drives moving CUI through machines you do not control are restricted.

AC
Level 2
1 pt
Rev. 3: Withdrawn and incorporated elsewhere

The requirement, verbatim

NIST SP 800-171 Rev. 2 · 3.1.21
Limit use of portable storage devices on external systems.

Requirement 3.1.21, practice name in the CMMC assessment guide: Portable Storage Use.

NIST's discussion

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.

NIST SP 800-171 Rev. 2, discussion under 3.1.21. Whitespace normalised; wording unchanged.

Assessment objectives

An assessor decides each of these separately. The requirement is met only when every objective is.

[a] the use of portable storage devices containing CUI on external systems is identified
[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

NIST SP 800-171A, determination statements for 3.1.21.

For assessors: examine, interview, test

NIST SP 800-171A names what an assessor may examine, whom they may interview, and what they may test for this requirement. Assessors select from these lists; they are not a checklist of everything you must produce.

Examine

Access control policy
procedures addressing the use of external systems
system security plan
system design documentation
system configuration settings and associated documentation
system connection or processing agreements
system audit logs and records
other relevant documents or records

Interview

Personnel with responsibilities for restricting or prohibiting use of organization-controlled storage devices on external systems
system or network administrators
personnel with information security responsibilities

Test

Mechanisms restricting or prohibiting the use of portable storage devices on external systems

NIST SP 800-171A, potential assessment methods and objects for 3.1.21.

Evidence

No evidence examples are published for this requirement yet. The objectives above are what an assessor checks; evidence is whatever shows each one is true in your environment, dated and kept with your system security plan.

Scoring weight

Worth 1 point. Not meeting this requirement subtracts 1 from your 110-point SPRS score.

DoD NIST SP 800-171 Assessment Methodology v1.2.1 weighting, as carried in the Bedrock scoring table. The score starts at 110 and subtracts the weight of every requirement not met.

In Rev. 3

Rev. 2 is what your contract requires today. A standing DoD class deviation keeps Rev. 2 in force; NIST has published Rev. 3, but it is not adopted for contracts. In Rev. 3 this requirement is withdrawn and incorporated elsewhere: 03.01.20 Use of External Systems.

See the Rev. 2 and Rev. 3 wording word by word, or start with the status page.

Where this page's facts come from

Requirement text: bedrock-cmmc-api@89b8e8e:migrations/004_reference_requirements.sql#Requirement.basicRequirement@rev2
Discussion: bedrock-cmmc-api@89b8e8e:migrations/004_reference_requirements.sql#Requirement.discussion@rev2
Practice name: bedrock-cmmc-api@89b8e8e:migrations/004_reference_requirements.sql#Requirement.title@rev2 (CMMC Assessment Guide practice name)
Objectives: bedrock-cmmc-api@89b8e8e:migrations/005_reference_objectives.sql#AssessmentObjective.description@rev2
Examine, interview, test: bedrock-cmmc-api@89b8e8e:migrations/005_reference_objectives.sql#AssessmentObjective.description@rev2 ({examineGuidance, interviewGuidance, testGuidance})
Level: bedrock-cmmc-api@89b8e8e:migrations/021_fix_level1_requirements.sql#Requirement.cmmcLevel@rev2
Weight: bedrock-cmmc-api@89b8e8e:internal/cmmc/requirement_values.go#requirementValues (DoD AM v1.2.1 / eMASS L2 template v3.8)
Rev. 3 mapping: bedrock-cmmc-api@89b8e8e:docs/reference/nist-800-171-rev3/normalized/r2_r3_transition_map.json#r2_to_r3
Plain-language title and summary: editorial/CMMC Navigator.dc.html#RAW (Foxx Cyber editorial)