Adversaries may use bootkits to persist on systems and evade detection. Bootkits reside at a layer below the operating system and may make it difficult to perform full remediation unless an organization suspects one was used and can act accordingly.
Use threat modeling, attack surface analysis, and vulnerability analysis to inform the current development process using analysis from similar systems, components, or services where applicable. Reduce attack surface where possible based on threats.
Vulnerability scanning is used to identify known software vulnerabilities (excluding custom-developed software - ex: COTS and Open-Source). Utilize scanning tools to identify vulnerabilities in dependencies and outdated software (i.e., software composition analysis). Ensure that vulnerability scanning tools and techniques are employed that facilitate interoperability among tools and automate parts of the vulnerability management process by using standards for: (1) Enumerating platforms, custom software flaws, and improper configurations; (2) Formatting checklists and test procedures; and (3) Measuring vulnerability impact.
Generate Software Bill of Materials (SBOM) against the entire software supply chain and cross correlate with known vulnerabilities (e.g., Common Vulnerabilities and Exposures) to mitigate known vulnerabilities. Protect the SBOM according to countermeasures in CM0001.
Create prioritized list of software weakness classes (e.g., Common Weakness Enumerations), based on system-specific considerations, to be used during static code analysis for prioritization of static analysis results.
Define acceptable coding standards to be used by the software developer. The mission should have automated means to evaluate adherence to coding standards. The coding standard should include the acceptable software development language types as well. The language should consider the security requirements, scalability of the application, the complexity of the application, development budget, development time limit, application security, available resources, etc. The coding standard and language choice must ensure proper security constructs are in place.
Employ dynamic analysis (e.g., using simulation, penetration testing, fuzzing, etc.) to identify software/firmware weaknesses and vulnerabilities in developed and incorporated code (open source, commercial, or third-party developed code). Testing should occur (1) on potential system elements before acceptance; (2) as a realistic simulation of known adversary tactics, techniques, procedures (TTPs), and tools; and (3) throughout the lifecycle on physical and logical systems, elements, and processes. FLATSATs as well as digital twins can be used to perform the dynamic analysis depending on the TTPs being executed. Digital twins via instruction set simulation (i.e., emulation) can provide robust environment for dynamic analysis and TTP execution.
Perform static source code analysis for all available source code looking for system-relevant weaknesses (see CM0016) using no less than two static code analysis tools.
Prevent the installation of Flight Software without verification that the component has been digitally signed using a certificate that is recognized and approved by the mission.
Ensure spacecraft's operating system is scrutinized/whitelisted and has received adequate software assurance previously. The operating system should be analyzed for its attack surface and non-utilized features should be stripped from the operating system. Many real-time operating systems contain features that are not necessary for spacecraft operations and only increase the attack surface.
Utilize on-board intrusion detection/prevention system that monitors the mission critical components or systems and audit/logs actions. The IDS/IPS should have the capability to respond to threats (initial access, execution, persistence, evasion, exfiltration, etc.) and it should address signature-based attacks along with dynamic never-before seen attacks using machine learning/adaptive technologies. The IDS/IPS must integrate with traditional fault management to provide a wholistic approach to faults on-board the spacecraft. Spacecraft should select and execute safe countermeasures against cyber-attacks. These countermeasures are a ready supply of options to triage against the specific types of attack and mission priorities. Minimally, the response should ensure vehicle safety and continued operations. Ideally, the goal is to trap the threat, convince the threat that it is successful, and trace and track the attacker — with or without ground support. This would support successful attribution and evolving countermeasures to mitigate the threat in the future. “Safe countermeasures” are those that are compatible with the system’s fault management system to avoid unintended effects or fratricide on the system.
Ensure fault management system cannot be used against the spacecraft. Examples include: safe mode with crypto bypass, orbit correction maneuvers, affecting integrity of telemetry to cause action from ground, or some sort of proximity operation to cause spacecraft to go into safe mode. Understanding the safing procedures and ensuring they do not put the spacecraft in a more vulnerable state is key to building a resilient spacecraft.
Provide the capability to enter the spacecraft into a configuration-controlled and integrity-protected state representing a known, operational cyber-safe state (e.g., cyber-safe mode). Spacecraft should enter a cyber-safe mode when conditions that threaten the platform are detected. Cyber-safe mode is an operating mode of a spacecraft during which all nonessential systems are shut down and the spacecraft is placed in a known good state using validated software and configuration settings. Within cyber-safe mode, authentication and encryption should still be enabled. The spacecraft should be capable of reconstituting firmware and software functions to pre-attack levels to allow for the recovery of functional capabilities. This can be performed by self-healing, or the healing can be aided from the ground. However, the spacecraft needs to have the capability to replan, based on equipment still available after a cyber-attack. The goal is for the spacecraft to resume full mission operations. If not possible, a reduced level of mission capability should be achieved. Cyber-safe mode software/configuration should be stored onboard the spacecraft in memory with hardware-based controls and should not be modifiable.
Software/Firmware must verify a trust chain that extends through the hardware root of trust, boot loader, boot configuration file, and operating system image, in that order. The trusted boot/RoT computing module should be implemented on radiation tolerant burn-in (non-programmable) equipment.