Two-Person Rule

Techniques Addressed by Countermeasure

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ID		Name	Description
IA-0007		Compromise Ground Station	Threat actors may initially compromise the ground station in order to access the target SV. 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.
	.01	Compromise On-Orbit Update	Threat actors may manipulate and modify on-orbit updates before they are sent to the target SV. 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.
	.02	Malicious Commanding via Valid GS	Threat actors may compromise target owned ground systems components (e.g., front end processors, command and control software, etc.) that can be used for future campaigns or to perpetuate other techniques. These ground systems components have already been configured for communications to the victim SV. By compromising this infrastructure, threat actors can stage, launch, and execute an operation. Threat actors may utilize these systems for various tasks, including Execution and Exfiltration.
DE-0004		Masquerading	Threat actors may gain access to a victim SV by masquerading as an authorized entity. This can be done several ways, including through the manipulation of command headers, spoofing locations, or even leveraging Insider's access (i.e., Insider Threat)

Space Threats Addressed by Countermeasure

ID	Description

Low-Level Requirements

Requirement	Rationale/Additional Guidance/Notes
The [organization] shall develop and document program-specific access control policies for controlling information flow and leakage on-board the spacecraft.{AC-1,AC-3,AC-3(3),AC-3(4),AC-3(13)}
The [organization] shall ensure any update to on-board software, memory, or stored procedures has met high assurance standards before execution. {AC-3(2),CM-3,SA-8(8),SA-8(31),SA-10(2),SR-4(4)}
The [organization] shall have a two-man rule to achieve a high level of security for systems with command level access to the spacecraft.(Under this rule all access and actions require the presence of two authorized people at all times.) {SV-AC-4}{PE-3}	Note: These are not spacecraft requirements but important to call out but likely are covered under other requirements by the customer.
The [organization] shall have physical security controls to prevent unauthorized access to the systems that have the ability to command the spacecraft.{SV-AC-4}{PE-3}	Note: These are not spacecraft requirements but important to call out but likely are covered under other requirements by the customer.
The [spacecraft] shall enforce an attribute-based access control policy over subjects and objects as defined in AC-3(3).{AC-3(13)}
The [spacecraft] shall require multi-factor authorization for all updates to the task scheduling functionality within the spacecraft.{SV-AV-4}{AC-3(2)}	Multi-factor authorization could be the "two-man rule" where procedures are in place to prevent a successful attack by a single actor (note: development activities that are subsequently subject to review or verification activities may already require collaborating attackers such that a "two-man rule" is not appropriate).
The [spacecraft] shall require multi-factor authorization for new and updates to on-board stored command sequences.{SV-IT-5}{AC-3(2)}	Multi-factor authorization could be the "two-man rule" where procedures are in place to prevent a successful attack by a single actor (note: development activities that are subsequently subject to review or verification activities may already require collaborating attackers such that a "two-man rule" is not appropriate).
The [spacecraft] software subsystems shall provide non-identical methods, or functionally independent methods, for commanding a mission critical function when the software is the sole control of that function.{SV-MA-3,SV-AV-7}{AC-3(2)}
The [spacecraft] software subsystems shall provide two independent and unique command messages to deactivate a fault tolerant capability for a critical or catastrophic hazard.{SV-MA-3,SV-AV-7}{AC-3(2)}
The [spacecraft] shall require multi-factor authorization for all spacecraft [applications or operating systems] updates within the spacecraft.{SV-SP-9,SV-SP-11}{AC-3(2),CM-3(8),CM-5,PM-12,SA-8(8),SA-8(31),SA-10(2),SI-3(8),SI-7(12),SI-10(6)}	The intent is for multiple checks to be performed prior to executing these SV SW updates. One action is mere act of uploading the SW to the spacecraft. Another action could be check of digital signature (ideal but not explicitly required) or hash or CRC or a checksum. Crypto boxes provide another level of authentication for all commands, including SW updates but ideally there is another factor outside of crypto to protect against FSW updates. Multi-factor authorization could be the "two-man rule" where procedures are in place to prevent a successful attack by a single actor (note: development activities that are subsequently subject to review or verification activities may already require collaborating attackers such that a "two-man rule" is not appropriate).
The [spacecraft] shall provide two independent and unique command messages to deactivate a fault tolerant capability for a critical or catastrophic hazard.{AC-3(2),PE-10,SA-8(15)}
The [spacecraft] shall provide non-identical methods, or functionally independent methods, for commanding a mission critical function when the software is the sole control of that function.{AC-3(2),SI-3(8),SI-13}
All [spacecraft] commands which have unrecoverable consequence must have dual authentication prior to command execution.{AU-9(5),IA-3,IA-4,IA-10,PE-3,PM-12,SA-8(15),SA-8(21),SC-16(2),SC-16(3),SI-3(8),SI-3(9),SI-4(13),SI-4(25),SI-7(12),SI-10(6),SI-13}
The [spacecraft] shall have a method to ensure the integrity of these commands and validate their authenticity before execution.{AU-9(5),IA-3,IA-4,IA-10,PE-3,PM-12,SA-8(15),SA-8(21),SC-16(2),SC-16(3),SI-3(8),SI-3(9),SI-4(13),SI-4(25),SI-7(12),SI-10(6),SI-13}