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SA-8(3) SA · System and Services Acquisition

Modularity and Layering

LOW MODERATE HIGH
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Requirements NIST SOURCE

Implement the security design principles of modularity and layering in [organization-defined systems or system components].

Discussion (NIST Supplemental Guidance)

The principles of modularity and layering are fundamental across system engineering disciplines. Modularity and layering derived from functional decomposition are effective in managing system complexity by making it possible to comprehend the structure of the system. Modular decomposition, or refinement in system design, is challenging and resists general statements of principle. Modularity serves to isolate functions and related data structures into well-defined logical units. Layering allows the relationships of these units to be better understood so that dependencies are clear and undesired complexity can be avoided. The security design principle of modularity extends functional modularity to include considerations based on trust, trustworthiness, privilege, and security policy. Security-informed modular decomposition includes the allocation of policies to systems in a network, separation of system applications into processes with distinct address spaces, allocation of system policies to layers, and separation of processes into subjects with distinct privileges based on hardware-supported privilege domains.

Implementation Guidance

Engineering Interpretation

Original engineering commentary written for this explorer — not NIST source text and not authoritative guidance.

No engineering interpretation has been authored for SA-8(3) yet. This section is architected to receive it — see the Requirements and Assessment sections above for the authoritative NIST source content in the meantime.

Assessment

NIST SP 800-53A REV 5.2.0

Assessment Objectives

  1. systems or system components that implement the security design principle of modularity are defined;
  2. systems or system components that implement the security design principle of layering are defined;
  3. <SA-08(03)_ODP[01] systems or system components> implement the security design principle of modularity;
  4. <SA-08(03)_ODP[02] systems or system components> implement the security design principle of layering.

Examine

[SELECT FROM: System and services acquisition policy; procedures addressing the security design principles of modularity and layering used in the specification, design, development, implementation, and modification of the system; system design documentation; security and privacy requirements and specifications for the system; system security and privacy architecture; system security plan; other relevant documents or records].

Interview

[SELECT FROM: Organizational personnel with the responsibility for determining system security and privacy requirements; organizational personnel with system specification, design, development, implementation, and modification responsibilities; system developers; organizational personnel with information security responsibilities].

Test

[SELECT FROM: Organizational processes for applying the security design principles of modularity and layering in system specification, design, development, implementation, and modification; mechanisms supporting the application of the security design principles of modularity and layering in system specification, design, development, implementation, and modification; mechanisms supporting and/or implementing an isolation boundary].

Overlays

Showing the OT/ICS overlay for the parent control SA-8 — see the SA-8(3) entries within each baseline below.

OT/ICS Overlay SP 800-82r3

NIST SP 800-82r3 Appendix F, Table 22. Blank baseline means the control/control enhancement is not selected in that initial OT baseline.

LOW

  • Base control: Included (matches standard baseline)

MODERATE

  • Base control: Included (matches standard baseline)

HIGH

  • Base control: Included (matches standard baseline)

STIGs & CCIs

No STIG checks or CCI mappings are currently loaded for SA-8(3). This section is architected to display, per product: STIG ID, Finding ID, Severity, Title, Description, Check, Fix, CCI, and NIST control mapping — but nothing is populated here until a real DISA STIG/CCI dataset is ingested.

Learn more about STIG/CCI integration →

Evidence

Potential Evidence — Derived

Categorized from the SP 800-53A "Examine"/"Test" artifact list above by keyword — not an authoritative NIST evidence list.

Policy

  • System and services acquisition policy
  • system security plan

Configuration

  • system design documentation
  • system security and privacy architecture

Testing

  • Organizational processes for applying the security design principles of modularity and layering in system specification, design, development, implementation, and modification
  • mechanisms supporting the application of the security design principles of modularity and layering in system specification, design, development, implementation, and modification
  • mechanisms supporting and/or implementing an isolation boundary

Other Records

  • procedures addressing the security design principles of modularity and layering used in the specification, design, development, implementation, and modification of the system
  • security and privacy requirements and specifications for the system
  • other relevant documents or records