CMMC Navigatorby Foxx Cyber Bedrock CMMC

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3.13.5Put public services in their own subnet

Anything internet-facing sits in a DMZ, separated from internal systems.

The requirement, verbatim

NIST SP 800-171 Rev. 2 · 3.13.5

Implement subnetworks for publicly accessible system components that are physically or logically separated from internal networks.

Requirement 3.13.5, practice name in the CMMC assessment guide: Public-Access System Separation.

NIST's discussion

Subnetworks that are physically or logically separated from internal networks are referred to as demilitarized zones (DMZs). DMZs are typically implemented with boundary control devices and techniques that include routers, gateways, firewalls, virtualization, or cloud-based technologies.

NIST SP 800-41 provides guidance on firewalls and firewall policy. SP 800-125B provides guidance on security for virtualization technologies.

NIST SP 800-171 Rev. 2, discussion under 3.13.5. Whitespace normalised; wording unchanged.

Assessment objectives

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

  1. [a] publicly accessible system components are identified
  2. [b] subnetworks for publicly accessible system components are separated from internal organizational networks

NIST SP 800-171A, determination statements for 3.13.5.

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
  • System and communications protection policy
  • procedures addressing boundary protection
  • system security plan
  • list of key internal boundaries of the system
  • system design documentation
  • boundary protection hardware and software
  • system configuration settings and associated documentation
  • enterprise security architecture documentation
  • system audit logs and records
  • other relevant documents or records
Interview
  • System or network administrators
  • personnel with information security responsibilities
  • system developers
  • personnel with boundary protection responsibilities
Test
  • Mechanisms implementing boundary protection capability

NIST SP 800-171A, potential assessment methods and objects for 3.13.5.

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 withdrawn and incorporated elsewhere: 03.13.01 Boundary Protection.

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)