Segmentation

Segmentation establishes physical or logical isolation boundaries between spacecraft system components and functional domains to limit the propagation of compromise, contain the consequences of a security failure, and enforce controlled information flow across the mission architecture. Mission-critical functions must be isolated from non-mission-critical functions through enforced partition boundaries that control access to and protect the integrity of the hardware, software, and firmware implementing those functions. Information flow between partitioned components or applications must be explicitly authorized by security policy; any flow not affirmatively permitted is denied by default. Boundary protections must be implemented to separate spacecraft bus, communications, and payload components, preventing a compromise in one domain from directly affecting the others. Information crossing the spacecraft boundary shall receive confidentiality protection where required by its classification, sensitivity, or mission risk. Command-bearing and other security-critical exchanges shall receive the mission-required authentication, integrity, authorization, and anti-replay protections regardless of whether confidentiality is required. These controls collectively implement a defense-in-depth architecture in which an adversary who gains a foothold in one partition faces enforced barriers before reaching mission-critical assets.

Sources

ID: CM0038
Tier: I
Onboard SV CM 
Created: 2022/10/19
Last Modified: 2026/08/06

Pre-Operations Government

Acquisition requirements should mandate a documented segmentation architecture as a system security deliverable, identifying each isolation boundary, the components and functional domains it separates, and the access and information flow controls enforced at each boundary. Requirements should specify that mission-critical functionality be isolated from non-mission-critical functionality through enforced partition boundaries rather than procedural or administrative controls alone. Boundary enforcement must reside outside the control of software operating within the partition and must prevent that software from modifying or bypassing the applicable information flow policy. Contract language should require that the security policy governing information flow between partitions be documented, reviewed, and approved by government technical authorities before the architecture is finalized, and that any proposed information flow not explicitly authorized by the approved policy be prohibited by default in the implemented system. Verification should include testing that confirms partition isolation through adversarial attempts to cross boundaries without authorization, demonstration that unauthorized information flows are blocked, and confirmation that all data leaving the spacecraft boundary is encrypted in the operational configuration. Flow-down provisions should require subcontractors contributing components that span or interface with partition boundaries to implement boundary controls consistent with the approved segmentation architecture.

Pre-Operations Developer/Supplier

Segmentation architecture must be defined at the system design level before component designs are finalized, as partition boundaries implemented in hardware or at the hypervisor and operating system level are significantly more robust and less costly to establish during initial design than to retrofit into an integrated system. The segmentation design should be informed by the mission’s criticality analysis, with partition boundaries used to isolate higher-criticality components and functions from lower-trust or lower-criticality elements. Access from external interfaces to critical functions must be mediated through approved boundary controls rather than provided through direct paths. Partition enforcement mechanisms should be selected based on the required assurance level, system architecture, and consequences of boundary failure. Hardware-enforced separation, memory protection, separation kernels, and software-enforced mechanisms may be used individually or in combination, provided the selected implementation delivers the required isolation and policy-enforcement assurance. The information flow policy must be expressed formally enough to be implemented consistently in the access control logic at each boundary, with each permitted flow documented with its authorization basis and each denied flow confirmed as blocked through design and test. Boundary protections between bus, communications, and payload domains should prevent a compromise in one domain from directly propagating commands or data into another domain without traversing an enforced boundary control point.