SC-49 asks you to implement hardware enforced separation and policy enforcement between the security domains you define. NIST notes that system owners may need more strength of mechanism for specific threats and environments, and that hardware enforcement is stronger than software enforcement.
800-53 binds federal systems and contractors. Most commercial teams will meet this only through a contract or a high assurance program.
What it means in practice
You name the domains, then show that the boundary is held by hardware, such as a data diode or physically separate hosts, and not only by software rules.
Evidence to collect
- The list of domains and the reason each pair must be separated.
- Architecture diagrams showing the hardware element.
- Device inventory and configuration for that element.
Common gaps
Calling a VLAN or a virtual firewall hardware separation. Those are software mechanisms. See SC-50 for them.
How to implement it
Decide whether the threat justifies the cost. If it does, document the hardware path and test it. If not, SC-50 and SC-7 are the practical route.
Quick check
Is a VLAN hardware enforced separation?
No. It is a software mechanism. SC-49 is about stronger, hardware based separation.
