3.1.3Control where CUI is allowed to travel

Decide which systems and paths CUI may move along, and enforce it rather than trusting habit.

The requirement, verbatim

NIST SP 800-171 Rev. 2 · 3.1.3
Control the flow of CUI in accordance with approved authorizations.

Requirement 3.1.3, practice name in the CMMC assessment guide: Control CUI Flow.

NIST's discussion

Information flow control regulates where information can travel within a system and between systems (versus who can access the information) and without explicit regard to subsequent accesses to that information. Flow control restrictions include the following: keeping export-controlled information from being transmitted in the clear to the internet; blocking outside traffic that claims to be from within the organization; restricting requests to the internet that are not from the internal web proxy server; and limiting information transfers between organizations based on data structures and content.

Organizations commonly use information flow control policies and enforcement mechanisms to control the flow of information between designated sources and destinations (e.g., networks, individuals, and devices) within systems and between interconnected systems. Flow control is based on characteristics of the information or the information path. Enforcement occurs in boundary protection devices (e.g., gateways, routers, guards, encrypted tunnels, firewalls) that employ rule sets or establish configuration settings that restrict system services, provide a packet-filtering capability based on header information, or message-filtering capability based on message content (e.g., implementing key word searches or using document characteristics). Organizations also consider the trustworthiness of filtering and inspection mechanisms (i.e., hardware, firmware, and software components) that are critical to information flow enforcement.

Transferring information between systems representing different security domains with different security policies introduces risk that such transfers violate one or more domain security policies.

Organizations consider the shared nature of commercial telecommunications services in the implementation of security requirements associated with the use of such services. Commercial telecommunications services are commonly based on network components and consolidated management systems shared by all attached commercial customers and may also include third party-provided access lines and other service elements. Such transmission services may represent sources of increased risk despite contract security provisions. NIST SP 800-41 provides guidance on firewalls and firewall policy. SP 800-125B provides guidance on security for virtualization technologies.

In such situations, information owners or stewards provide guidance at designated policy enforcement points between interconnected systems. Organizations consider mandating specific architectural solutions when required to enforce specific security policies. Enforcement includes: prohibiting information transfers between interconnected systems (i.e., allowing access only); employing hardware mechanisms to enforce one-way information flows; and implementing trustworthy regrading mechanisms to reassign security attributes and security labels.

NIST SP 800-171 Rev. 2, discussion under 3.1.3. Whitespace normalised; wording unchanged.

Assessment objectives

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

[a] information flow control policies are defined
[b] methods and enforcement mechanisms for controlling the flow of CUI are defined
[c] designated sources and destinations (e.g., networks, individuals, and devices) for CUI within the system and between interconnected systems are identified
[d] authorizations for controlling the flow of CUI are defined
[e] approved authorizations for controlling the flow of CUI are enforced

NIST SP 800-171A, determination statements for 3.1.3.

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
information flow control policies
procedures addressing information flow enforcement
system security plan
system design documentation
system configuration settings and associated documentation
system baseline configuration
list of information flow authorizations
system audit logs and records
other relevant documents or records

Interview

System or network administrators
personnel with information security responsibilities
system developers

Test

Mechanisms implementing information flow enforcement policy

NIST SP 800-171A, potential assessment methods and objects for 3.1.3.

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 no significant change: 03.01.03 Information Flow Enforcement.

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)