Detection of larger-than-expected data packets sent during scheduled spacecraft communication windows, indicating that a compromised ground system may be exfiltrating data under the guise of legitimate operations.

STIX Pattern

[network-traffic:direction = 'downlink' AND network-traffic:data_size > 'expected_size']

SPARTA TTPs

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.
IA-0009	Trusted Relationship	Access through trusted third-party relationship exploits an existing connection that has been approved for interconnection. Leveraging third party / approved interconnections to pivot into the target systems is a common technique for threat actors as these interconnections typically lack stringent access control due to the trusted status.
IA-0009.01	Mission Collaborator (academia, international, etc.)	Threat actors may seek to exploit mission partners to gain an initial foothold for pivoting into the mission environment and eventually impacting the SV. The complex nature of many space systems rely on contributions across organizations, including academic partners and even international collaborators. These organizations will undoubtedly vary in their system security posture and attack surface.
IA-0009.02	Vendor	Threat actors may target the trust between vendors and the target space vehicle. Missions often grant elevated access to vendors in order to allow them to manage internal systems as well as cloud-based environments. The vendor's access may be intended to be limited to the infrastructure being maintained but it may provide laterally movement into the target space vehicle. Attackers may leverage security weaknesses in the vendor environment to gain access to more critical mission resources or network locations. In the space vehicle context vendors may have direct commanding and updating capabilities outside of the primary communication channel.
EXF-0001	Replay	Threat actors may exfiltrate data by replaying commands and capturing the telemetry or payload data as it is sent down. One scenario would be the threat actor replays commands to downlink payload data once SV is within certain location so the data can be intercepted on the downlink by threat actor ground terminals.
EXF-0003.02	Downlink Intercept	Threat actors may target the downlink connection from the victim SV in order to exfiltrate telemetry or payload data. This data can include health information of the SV or whatever mission data that is being collected/analyzed on the SV.
EXF-0007	Compromised Ground Station	Threat actors may compromise target owned ground systems that can be used for future campaigns or to perpetuate other techniques. These ground systems 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.
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 SV is in orbit, with the hopes of adding malicious code to the actual FSW during the development process.
EXF-0009	Compromised Partner Site	Threat actors may compromise access to partner sites that can be used for future campaigns or to perpetuate other techniques. These sites are typically configured for communications to the primary ground station(s) or in some cases the SV itself. Unlike mission operated ground systems, partner sites may provide an easier target for threat actors depending on the company, roles and responsibilities, and interests of the third-party. 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.