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Controls / System and Communications Protection / 3.13.1
3.13.1
SC.L1-3.13.1 · Level 1 + 2

Monitor, control, and protect communications (i.e., information transmitted or received by…

NIST SP 800-171 Rev 2 · §3.13.1

Monitor, control, and protect communications (i.e., information transmitted or received by organizational systems) at the external boundaries and key internal boundaries of organizational systems.

Assessment objectives

From NIST SP 800-171A · 8 objectives must be met to satisfy this control
3.13.1[a] the external system boundary is defined.
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; enterprise security architecture documentation; system audit logs and records; system configuration settings and associated documentation; 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].
3.13.1[b] key internal system boundaries are defined.
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; enterprise security architecture documentation; system audit logs and records; system configuration settings and associated documentation; 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].
3.13.1[c] communications are monitored at the external system boundary.
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; enterprise security architecture documentation; system audit logs and records; system configuration settings and associated documentation; 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].
3.13.1[d] communications are monitored at key internal boundaries.
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; enterprise security architecture documentation; system audit logs and records; system configuration settings and associated documentation; 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].
3.13.1[e] communications are controlled at the external system boundary.
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; enterprise security architecture documentation; system audit logs and records; system configuration settings and associated documentation; 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].
3.13.1[f] communications are controlled at key internal boundaries.
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; enterprise security architecture documentation; system audit logs and records; system configuration settings and associated documentation; 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].
3.13.1[g] communications are protected at the external system boundary.
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; enterprise security architecture documentation; system audit logs and records; system configuration settings and associated documentation; 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].
3.13.1[h] communications are protected at key internal boundaries.
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; enterprise security architecture documentation; system audit logs and records; system configuration settings and associated documentation; 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.