CMMC Navigatorby Foxx Cyber Bedrock CMMC

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3.4.8Decide what software may run

Either block what is known bad or, better, only allow what is approved.

The requirement, verbatim

NIST SP 800-171 Rev. 2 · 3.4.8

Apply deny-by-exception (blacklisting) policy to prevent the use of unauthorized software or deny-all, permit-by-exception (whitelisting) policy to allow the execution of authorized software.

Requirement 3.4.8, practice name in the CMMC assessment guide: Application Execution Policy.

NIST's discussion

The process used to identify software programs that are not authorized to execute on systems is commonly referred to as blacklisting. The process used to identify software programs that are authorized to execute on systems is commonly referred to as whitelisting. Whitelisting is the stronger of the two policies for restricting software program execution. In addition to whitelisting, organizations consider verifying the integrity of whitelisted software programs using, for example, cryptographic checksums, digital signatures, or hash functions. Verification of whitelisted software can occur either prior to execution or at system startup.

NIST SP 800-167 provides guidance on application whitelisting.

NIST SP 800-171 Rev. 2, discussion under 3.4.8. Whitespace normalised; wording unchanged.

Assessment objectives

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

  1. [a] a policy specifying programs authorized or not authorized to execute on the system is defined
  2. [b] the policy specifying programs authorized or not authorized to execute on the system is enforced

NIST SP 800-171A, determination statements for 3.4.8.

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
  • Configuration management policy
  • procedures addressing least functionality in the system
  • system security plan
  • configuration management plan
  • system design documentation
  • system configuration settings and associated documentation
  • list of software programs not authorized to execute on the system
  • list of software programs authorized to execute on the system
  • security configuration checklists
  • review and update records associated with list of authorized or unauthorized software programs
  • change control records
  • system audit logs and records
  • other relevant documents or records
Interview
  • Personnel with responsibilities for identifying software authorized or not authorized to execute on the system
  • personnel with information security responsibilities
  • system or network administrators
Test
  • Organizational process for identifying, reviewing, and updating programs authorized or not authorized to execute on the system
  • process for implementing blacklisting or whitelisting
  • mechanisms supporting or implementing blacklisting or whitelisting

NIST SP 800-171A, potential assessment methods and objects for 3.4.8.

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 5 points. Not meeting this requirement subtracts 5 from your 110-point SPRS score. These are the requirements with the largest effect on your posture.

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 reworded: 03.04.08 Authorized Software – Allow by Exception. It gains organization-defined parameters.

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)