3.13.5
SC.L1-3.13.5 · Level 1 + 2
Implement subnetworks for publicly accessible system components that are physically or logically…
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.
Assessment objectives
From NIST SP 800-171A · 2 objectives must be met to satisfy this control
Examine
[SELECT FROM: System and communications protection policy; procedures addressing boundary protection; 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
[SELECT FROM: System or network administrators; personnel with information security responsibilities; system developer; personnel with boundary protection responsibilities].
Test
[SELECT FROM: Mechanisms implementing boundary protection capability].
Examine
[SELECT FROM: System and communications protection policy; procedures addressing boundary protection; 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
[SELECT FROM: System or network administrators; personnel with information security responsibilities; system developer; personnel with boundary protection responsibilities].
Test
[SELECT FROM: Mechanisms implementing boundary protection capability].
What we look for in practice
The following are placeholder notes that should be refined based on practice experience.
What assessors look for in practice. Documented evidence that this control is implemented across all CUI-handling systems within scope. Specific artifacts vary, but expect requests for written procedures, system configurations, and operational records demonstrating the control is active.
Common failure patterns. Typical issues include incomplete documentation, inconsistent implementation across systems, and missing periodic review records. Refine this section as your practice accumulates direct assessment experience.
Strong evidence looks like. Formal policy referencing this control, technical configurations demonstrating enforcement, periodic review logs with sign-off, and procedures for handling exceptions.
Scoring and POA&M context. 5-point control under the DoD Assessment Methodology. Highest scoring impact — treat as a foundational requirement. Not POA&M-eligible — must be implemented at assessment time.