CM0040 Shared Resource Leakage Shared system resources (e.g., processor registers, main memory, secondary storage, cache) may retain residual data or security-relevant state after a process releases them for reuse. If a subsequent process can access that residual information, it may obtain data from the prior process, including sensitive information or encrypted representations of information that were not intended to cross process or partition boundaries. This countermeasure requires that shared resources be sanitized, zeroed, or otherwise cleared of prior process data before being allocated to a new process, ensuring that information transfer between processes occurs only through explicitly authorized channels. The protection must apply to encrypted representations as well as plaintext because encrypted data remains information belonging to the prior process and must not be transferred to another process solely because its contents are not immediately readable. This is particularly significant in space system environments where multiple processes of varying criticality and trust levels may share the same hardware resources.
CM0011 Vulnerability Scanning Vulnerability scanning systematically identifies known security weaknesses in commercial off-the-shelf (COTS) and open-source software (OSS) components, including vulnerable dependencies and outdated software versions, across spacecraft and ground system environments. Custom-developed code requires separate analysis approaches, such as static and dynamic code analysis, that fall outside the scope of this countermeasure; however, COTS, OSS, and third-party dependencies incorporated into custom-developed software remain within the scope of vulnerability scanning and SCA. Scanning programs should incorporate software composition analysis (SCA) to detect vulnerabilities introduced through third-party libraries and dependency chains, which represent a significant and frequently underestimated attack surface in modern space systems. Scanning tools and processes should conform to recognized interoperability standards that support enumeration of platforms, software flaws, and configuration weaknesses; standardized formatting of checklists and test procedures; and consistent measurement of vulnerability impact. Adherence to these standards enables automation of key vulnerability management workflow steps, facilitates tool interoperability across the mission ecosystem, and produces outputs that are comparable across programs and organizations.
Vulnerability scanning shall be performed against the approved as-built or deployed software baseline using methods that do not jeopardize mission operations. Active scanning of live spacecraft, safety-critical ground systems, or operational technology should occur only after the scanning method has been authorized and evaluated for operational impact. Where live scanning presents unacceptable risk, scanning should be performed against representative software images, firmware packages, or test environments that match the approved operational baseline.
CM0015 Software Source Control Binary or machine-executable code obtained from sources that provide no warranty and no access to the corresponding source code must not be incorporated into spacecraft or ground systems. This prohibition addresses a fundamental software assurance gap: without source code, missions cannot perform source-based static analysis or independently review and modify implementation details, and may have reduced ability to assess, repair, or extend the software. Code from sources with limited or no warranty and no source code provision may be difficult to independently analyze, repair, or extend and leaves the mission dependent on supplier assurances and remediation capabilities. This countermeasure applies throughout the software supply chain, including components integrated by subcontractors.
CM0018 Dynamic Testing Dynamic analysis subjects executing software and firmware to active testing conditions to identify weaknesses and vulnerabilities that static analysis alone cannot detect, including runtime memory corruption, logic errors, timing vulnerabilities, and interface behaviors that only manifest under operational conditions. Applicable techniques include simulation-based testing, penetration testing, fuzz testing, and adversarial emulation using realistic threat actor tactics, techniques, and procedures (TTPs). Dynamic testing must be applied to all software and firmware categories: mission-developed code, open-source components, commercial off-the-shelf (COTS) software, and third-party developed code. Dynamic testing should be performed on potential system elements before acceptance, include realistic simulation of known adversary TTPs, and tools, and continue throughout the lifecycle on applicable physical and logical systems, elements, and processes. Full-scale hardware integration testbeds, commonly referred to as flat satellite (FLATSAT) environments, provide high-fidelity physical test platforms for dynamic analysis; digital twins implemented via instruction set simulation, also known as emulation, provide a flexible and scalable alternative environment capable of supporting TTP execution across a broad range of test scenarios without requiring physical hardware availability.
CM0021 Software Digital Signature Each software or firmware image subject to installation or update control shall be verified using an approved digital signature and an approved trust anchor before installation or activation. The trust anchor may be represented by a certificate or by a directly provisioned verification key, depending on the approved trust architecture. Successful verification establishes that the image was signed by an authorized signing identity and has not been modified since signing; it does not establish that the signed code is non-malicious, vulnerability-free, or operationally safe. Signature verification confirms the integrity and approved origin of the software but does not, by itself, prevent installation of an older validly signed version; update authorization and rollback protections must be enforced separately.
The verification mechanism must be implemented such that it cannot be bypassed through operational commands, configuration changes, or software updates, and must reject any component whose signature is absent or invalid, or whose signing certificate or trust anchor is not recognized and approved by the mission. Digital signature enforcement complements but is distinct from the boot-time chain of trust established through secure boot; it applies to software installation and update events throughout the operational lifecycle, not only at system startup.
CM0039 Least Privilege The principle of least privilege requires that every process, user account, service, and system component be granted only the permissions and access rights necessary to perform its defined function, with no additional privileges retained beyond what the assigned task requires. Applied to spacecraft and ground systems, this means that processes executing on flight computers, operating system services, ground system applications, and inter-system communication handlers are each confined to the minimum privilege level needed for their specific function, preventing a compromised or malfunctioning component from leveraging excess permissions to affect other system resources or functions. Separate execution domains should be used where supported to reinforce least privilege and contain process failures or compromise. Process isolation does not replace explicit access controls, because authorized communication and shared resources may still cross execution-domain boundaries. Least privilege is a foundational design principle that reduces the consequence of any individual component compromise by limiting what an adversary can accomplish within that component's execution context.
CM0069 Process White Listing Process whitelisting establishes an approved set of executable images, tasks, applications, or process types that may run on the spacecraft computing platform. Enforcement should occur within a trusted layer capable of controlling process or task creation, which may be implemented in firmware, a secure monitor, a hypervisor, the operating system, or the real-time executive according to the platform architecture. The enforcement mechanism must verify an approved process identity before execution and deny unapproved process creation unless a mission-approved recovery mechanism applies. This countermeasure limits the creation or execution of software identities not present in the approved baseline. It does not prevent an adversary from abusing an approved process, altering its runtime memory, redirecting its control flow, or exploiting permitted scripting or loading functionality unless those behaviors are addressed by complementary integrity and execution controls.
CM0032 On-board Intrusion Detection & Prevention An on-board intrusion detection and prevention system (IDS/IPS) monitors mission-critical spacecraft components and systems, generates and stores audit records, and supports mission-approved responses to detected threats. Depending on the mission architecture, threat, and availability of ground support, responses may be autonomous, ground-directed, or a combination of both. The system should address both known attack patterns and previously unseen anomalous behavior through complementary signature-based and behavior- or anomaly-based detection methods. Machine learning or adaptive technologies may be used when their performance, resource consumption, and failure behavior have been validated for the mission environment. Detection and response coverage should address applicable adversary activities across the attack lifecycle, including initial access, execution, persistence, defense evasion, and exfiltration. The on-board IDS/IPS must be integrated with the spacecraft's traditional fault management system to provide a unified approach to anomaly response, ensuring that cyber-triggered responses are compatible with fault management logic and do not produce unintended effects or fratricide against the spacecraft's own systems; countermeasures that are incompatible with fault management are considered unsafe and must not be executed autonomously. The response hierarchy must prioritize vehicle safety and continued mission operations. Advanced containment or deception responses may be considered when they can be executed without unacceptable mission risk. The system should preserve evidence that supports post-event analysis, threat characterization, and potential attribution by authorized ground support.