SC-7(29)—Boundary Protection | Separate Subnets to Isolate Functions
IL5
IL6
>Control Description
Implement ☑physically; logically separate subnetworks to isolate the following critical system components and functions: ⚙organization-defined critical system components and functions.
>DoD Impact Level Requirements
No specific parameter values or requirements for this impact level.
>Discussion
Separating critical system components and functions from other noncritical system components and functions through separate subnetworks may be necessary to reduce susceptibility to a catastrophic or debilitating breach or compromise that results in system failure. For example, physically separating the command and control function from the in-flight entertainment function through separate subnetworks in a commercial aircraft provides an increased level of assurance in the trustworthiness of critical system functions.
>Assessment Interview Topics
Questions assessors commonly ask
Process & Governance:
- •What policies govern the implementation of separate subnets to isolate functions?
- •How are system and communications protection requirements defined and maintained?
- •Who is responsible for configuring and maintaining the security controls specified in SC-7(29)?
Technical Implementation:
- •How is separate subnets to isolate functions technically implemented in your environment?
- •What systems, tools, or configurations enforce this protection requirement?
- •How do you ensure that separate subnets to isolate functions remains effective as the system evolves?
- •What network boundary protections are in place (firewalls, gateways, etc.)?
- •How is separation of duties or partitioning technically enforced?
Evidence & Documentation:
- •What documentation demonstrates the implementation of SC-7(29)?
- •Can you provide configuration evidence or system diagrams showing this protection control?
- •What logs or monitoring data verify that this control is functioning correctly?
- •Can you provide network architecture diagrams and firewall rulesets?
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