SA-8(3)—Security and Privacy Engineering Principles | Modularity and Layering
>Control Description
>DoD Impact Level Requirements
No specific parameter values or requirements for this impact level.
>Discussion
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.
>Related Controls
>Assessment Interview Topics
Questions assessors commonly ask
Process & Governance:
- •What acquisition policies and procedures address the requirements of SA-8(3)?
- •How are security and privacy requirements integrated into the acquisition process?
- •Who is responsible for ensuring that acquisitions comply with SA-8(3)?
Technical Implementation:
- •How are security requirements defined and documented in acquisition contracts?
- •What mechanisms ensure that acquired systems and services meet security requirements?
- •How do you validate that vendors and service providers comply with specified security controls?
Evidence & Documentation:
- •Can you provide examples of acquisition documentation that includes security requirements?
- •What evidence demonstrates that acquired systems meet security specifications?
- •Where is acquisition security documentation maintained throughout the system lifecycle?
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