SA-15(5) - Reference

SA-15(5) - Development Process, Standards, and Tools | Attack Surface Reduction

Require the developer of the system, system component, or system service to reduce attack surfaces to [Assignment: organization-defined thresholds].

ID: SA-15(5)

Enhancement of : SA-15

Space Segment Guidance

Reducing the attack surface in space vehicle development means systematically stripping away non-essential interfaces, code libraries, and services—both on the bus and within payload subsystems. This includes limiting external ports, ensuring that unneeded network protocols or legacy diagnostic features are disabled prior to launch, and refactoring complex software modules to remove extraneous dependencies. For instance, if a payload only needs to read specific sensor data, no write privileges should exist in memory segments storing flight control logic. In addition, employing microkernel architectures or containerization where feasible can isolate critical processes (e.g., cryptographic handling) from less trusted payload applications. By integrating these measures into design standards and building pipelines early, organizations can avoid the pitfalls of retrofitting security controls later, yielding more robust spacecraft that are harder for adversaries to compromise.

Countermeasures Covered by Control

ID		Name	Description	D3FEND
CM0004		Development Environment Security	In order to secure the development environment, the first step is understanding all the devices and people who interact with it. Maintain an accurate inventory of all people and assets that touch the development environment. Ensure strong multi-factor authentication is used across the development environment, especially for code repositories, as threat actors may attempt to sneak malicious code into software that's being built without being detected. Use zero-trust access controls to the code repositories where possible. For example, ensure the main branches in repositories are protected from injecting malicious code. A secure development environment requires change management, privilege management, auditing and in-depth monitoring across the environment.

Space Threats Tagged by Control

ID		Description
SV-SP-1		Exploitation of software vulnerabilities (bugs); Unsecure code, logic errors, etc. in the FSW.
SV-SP-6		Software reuse, COTS dependence, and standardization of onboard systems using building block approach with addition of open-source technology leads to supply chain threat
SV-SP-9		On-orbit software updates/upgrades/patches/direct memory writes. If TT&C is compromised or MOC or even the developer's environment, the risk exists to do a variation of a supply chain attack where after it is in orbit you inject malicious code
SV-SP-11		Software defined radios - SDR is also another computer, networked to other parts of the spacecraft that could be pivoted to by an attacker and infected with malicious code. Once access to an SDR is gained, the attacker could alter what the SDR thinks is correct frequencies and settings to communicate with the ground.
SV-SP-7		Software can be broken down into three levels (operating system and drivers’ layer, data handling service layer, and the application layer). Highest impact on system is likely the embedded code at the BIOS, kernel/firmware level. Attacking the on-board operating systems. Since it manages all the programs and applications on the computer, it has a critical role in the overall security of the system. Since threats may occur deliberately or due to human error, malicious programs or persons, or existing system vulnerability mitigations must be deployed to protect the OS.

Sample Requirements

Requirement	Rationale/Additional Guidance/Notes
The [organization] shall conduct an Attack Surface Analysis and reduce attack surfaces to a level that presents a low level of compromise by an attacker.{SV-SP-1,SV-SP-6,SV-SP-7,SV-SP-9,SV-SP-11}{SA-11(6),SA-15(5)}
The [organization] shall require the developer to conduct an attack surface analysis on the spacecraft architecture to identify and reduce attack surfaces (e.g.entry points) to the lowest possible level that still permits the system to meet performance requirements/mission objectives.{SA-11(6),SA-15(5)}
The [spacecraft] shall be configured to provide only essential capabilities.{CM-6,CM-7,SA-8(2),SA-8(7),SA-8(13),SA-8(23),SA-8(26),SA-15(5)}

Related SPARTA Techniques and Sub-Techniques

ID		Name	Description
REC-0006		Gather FSW Development Information	Threat actors may obtain information regarding the flight software (FSW) development environment for the victim spacecraft. This information may include the development environment, source code, compiled binaries, testing tools, and fault management.
	REC-0006.01	Development Environment	Threat actors may gather information regarding the development environment for the victim spacecraft's FSW. This information can include IDEs, configurations, source code, environment variables, source code repositories, code "secrets", and compiled binaries.
IA-0001		Compromise Supply Chain	Threat actors may manipulate or compromise products or product delivery mechanisms before the customer receives them in order to achieve data or system compromise.
	IA-0001.02	Software Supply Chain	Threat actors may manipulate software binaries and applications prior to the customer receiving them in order to achieve data or system compromise. This attack can take place in a number of ways, including manipulation of source code, manipulation of the update and/or distribution mechanism, or replacing compiled versions with a malicious one.
IA-0002		Compromise Software Defined Radio	Threat actors may target software defined radios due to their software nature to establish C2 channels. Since SDRs are programmable, when combined with supply chain or development environment attacks, SDRs provide a pathway to setup covert C2 channels for a threat actor.
IA-0006		Compromise Hosted Payload	Threat actors may compromise the target spacecraft hosted payload to initially access and/or persist within the system. Hosted payloads can usually be accessed from the ground via a specific command set. The command pathways can leverage the same ground infrastructure or some host payloads have their own ground infrastructure which can provide an access vector as well. Threat actors may be able to leverage the ability to command hosted payloads to upload files or modify memory addresses in order to compromise the system. Depending on the implementation, hosted payloads may provide some sort of lateral movement potential.
IA-0007		Compromise Ground System	Threat actors may initially compromise the ground system in order to access the target spacecraft. Once compromised, the threat actor can perform a multitude of initial access techniques, including replay, compromising FSW deployment, compromising encryption keys, and compromising authentication schemes. Threat actors may also perform further reconnaissance within the system to enumerate mission networks and gather information related to ground station logical topology, missions ran out of said ground station, birds that are in-band of targeted ground stations, and other mission system capabilities.
	IA-0007.01	Compromise On-Orbit Update	Threat actors may manipulate and modify on-orbit updates before they are sent to the target spacecraft. This attack can be done in a number of ways, including manipulation of source code, manipulating environment variables, on-board table/memory values, or replacing compiled versions with a malicious one.
IA-0012		Assembly, Test, and Launch Operation Compromise	Threat actors may target the spacecraft hardware and/or software while the spacecraft is at Assembly, Test, and Launch Operation (ATLO). ATLO is often the first time pieces of the spacecraft are fully integrated and exchanging data across interfaces. Malware could propagate from infected devices across the integrated spacecraft. For example, test equipment (i.e., transient cyber asset) is often brought in for testing elements of the spacecraft. Additionally, varying levels of physical security is in place which may be a reduction in physical security typically seen during development. The ATLO environment should be considered a viable attack vector and the appropriate/equivalent security controls from the primary development environment should be implemented during ATLO as well.
PER-0002		Backdoor	Threat actors may find and target various backdoors, or inject their own, within the victim spacecraft in the hopes of maintaining their attack.
	PER-0002.02	Software	Threat actors may inject code to create their own backdoor to establish persistent access to the spacecraft. This may be done through modification of code throughout the software supply chain or through modification of the software-defined radio configuration (if applicable).
LM-0001		Hosted Payload	Threat actors may use the hosted payload within the victim spacecraft in order to gain access to other subsystems. The hosted payload often has a need to gather and send data to the internal subsystems, depending on its purpose. Threat actors may be able to take advantage of this communication in order to laterally move to the other subsystems and have commands be processed.
EXF-0006		Modify Communications Configuration	Threat actors can manipulate communications equipment, modifying the existing software, hardware, or the transponder configuration to exfiltrate data via unintentional channels the mission has no control over.
	EXF-0006.01	Software Defined Radio	Threat actors may target software defined radios due to their software nature to setup exfiltration channels. Since SDRs are programmable, when combined with supply chain or development environment attacks, SDRs provide a pathway to setup covert exfiltration channels for a threat actor.
	EXF-0006.02	Transponder	Threat actors may change the transponder configuration to exfiltrate data via radio access to an attacker-controlled asset.
EXF-0008		Compromised Developer Site	Threat actors may compromise development environments located within the ground system or a developer/partner site. This attack can take place in a number of different ways, including manipulation of source code, manipulating environment variables, or replacing compiled versions with a malicious one. This technique is usually performed before the target spacecraft is in orbit, with the hopes of adding malicious code to the actual FSW during the development process.