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Controls / Security Assessment / 3.12.4
3.12.4
CA.L2-3.12.4 · Level 2

Develop, document, and periodically update system security plans that describe system boundaries,…

NIST SP 800-171 Rev 2 · §3.12.4

Develop, document, and periodically update system security plans that describe system boundaries, system environments of operation, how security requirements are implemented, and the relationships with or connections to other systems.

Assessment objectives

From NIST SP 800-171A · 8 objectives must be met to satisfy this control
3.12.4[a] a system security plan is developed.
Examine
[SELECT FROM: Security planning policy; procedures addressing security plan development and implementation; procedures addressing security plan reviews and updates; enterprise architecture documentation; security plan; records of security plan reviews and updates; other relevant documents or records].
Interview
[SELECT FROM: Personnel with security planning and plan implementation responsibilities; personnel with information security responsibilities].
Test
[SELECT FROM: Organizational processes for security plan development, review, update, and approval; mechanisms supporting the security plan].
3.12.4[b] the system boundary is described and documented in the system security plan.
Examine
[SELECT FROM: Security planning policy; procedures addressing security plan development and implementation; procedures addressing security plan reviews and updates; enterprise architecture documentation; security plan; records of security plan reviews and updates; other relevant documents or records].
Interview
[SELECT FROM: Personnel with security planning and plan implementation responsibilities; personnel with information security responsibilities].
Test
[SELECT FROM: Organizational processes for security plan development, review, update, and approval; mechanisms supporting the security plan].
3.12.4[c] the system environment of operation is described and documented in the system security plan.
Examine
[SELECT FROM: Security planning policy; procedures addressing security plan development and implementation; procedures addressing security plan reviews and updates; enterprise architecture documentation; security plan; records of security plan reviews and updates; other relevant documents or records].
Interview
[SELECT FROM: Personnel with security planning and plan implementation responsibilities; personnel with information security responsibilities].
Test
[SELECT FROM: Organizational processes for security plan development, review, update, and approval; mechanisms supporting the security plan].
3.12.4[d] the security requirements identified and approved by the designated authority as non-applicable are identified.
Examine
[SELECT FROM: Security planning policy; procedures addressing security plan development and implementation; procedures addressing security plan reviews and updates; enterprise architecture documentation; security plan; records of security plan reviews and updates; other relevant documents or records].
Interview
[SELECT FROM: Personnel with security planning and plan implementation responsibilities; personnel with information security responsibilities].
Test
[SELECT FROM: Organizational processes for security plan development, review, update, and approval; mechanisms supporting the security plan].
3.12.4[e] the method of security requirement implementation is described and documented in the system security plan.
Examine
[SELECT FROM: Security planning policy; procedures addressing security plan development and implementation; procedures addressing security plan reviews and updates; enterprise architecture documentation; security plan; records of security plan reviews and updates; other relevant documents or records].
Interview
[SELECT FROM: Personnel with security planning and plan implementation responsibilities; personnel with information security responsibilities].
Test
[SELECT FROM: Organizational processes for security plan development, review, update, and approval; mechanisms supporting the security plan].
3.12.4[f] the relationship with or connection to other systems is described and documented in the system security plan.
Examine
[SELECT FROM: Security planning policy; procedures addressing security plan development and implementation; procedures addressing security plan reviews and updates; enterprise architecture documentation; security plan; records of security plan reviews and updates; other relevant documents or records].
Interview
[SELECT FROM: Personnel with security planning and plan implementation responsibilities; personnel with information security responsibilities].
Test
[SELECT FROM: Organizational processes for security plan development, review, update, and approval; mechanisms supporting the security plan].
3.12.4[g] the frequency to update the system security plan is defined.
Examine
[SELECT FROM: Security planning policy; procedures addressing security plan development and implementation; procedures addressing security plan reviews and updates; enterprise architecture documentation; security plan; records of security plan reviews and updates; other relevant documents or records].
Interview
[SELECT FROM: Personnel with security planning and plan implementation responsibilities; personnel with information security responsibilities].
Test
[SELECT FROM: Organizational processes for security plan development, review, update, and approval; mechanisms supporting the security plan].
3.12.4[h] system security plans are updated with the defined frequency.
Examine
[SELECT FROM: Security planning policy; procedures addressing security plan development and implementation; procedures addressing security plan reviews and updates; enterprise architecture documentation; security plan; records of security plan reviews and updates; other relevant documents or records].
Interview
[SELECT FROM: Personnel with security planning and plan implementation responsibilities; personnel with information security responsibilities].
Test
[SELECT FROM: Organizational processes for security plan development, review, update, and approval; mechanisms supporting the security plan].

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. Special: SSP control. Absence of an SSP results in 'assessment could not be completed' per the DoD Assessment Methodology. Not POA&M-eligible — must be implemented at assessment time.