id: "SA-08(03)" title: "Modularity and Layering" family: "SA" family_name: "System and Services Acquisition" sort_id: "sa-08.03" priority: "P1" implementation_level: "system" parent: "SA-08" enhancement: True
Statement
Implement the security design principles of modularity and layering in {{ insert: param, sa-8.3_prm_1 }}.
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.
Assessment Objective: {{ insert: param, sa-08.03_odp.01 }} implement the security design principle of modularity;
Assessment Objective: {{ insert: param, sa-08.03_odp.02 }} implement the security design principle of layering.
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
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
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