CM-7(4) - Least Functionality | Unauthorized Software

(a) Identify [Assignment: organization-defined software programs not authorized to execute on the system]; (b) Employ an allow-all, deny-by-exception policy to prohibit the execution of unauthorized software programs on the system; and (c) Review and update the list of unauthorized software programs [Assignment: organization-defined frequency].


Informational References

ISO 27001

ID: CM-7(4)
Enhancement of : CM-7

Countermeasures Covered by Control

ID Name Description D3FEND
CM0010 Update Software Perform regular software updates to mitigate exploitation risk. Software updates may need to be scheduled around operational down times. Release updated versions of the software/firmware systems incorporating security-relevant updates, after suitable regression testing, at a frequency no greater than mission-defined frequency [i.e., 30 days]. Ideally old versions of software are removed after upgrading but restoration states (i.e., gold images) are recommended to remain on the system. D3-SU
CM0012 Software Bill of Materials 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. D3-AI D3-AVE D3-SWI
CM0039 Least Privilege Employ the principle of least privilege, allowing only authorized processes which are necessary to accomplish assigned tasks in accordance with system functions. Ideally maintain a separate execution domain for each executing process. D3-MAC D3-EI D3-HBPI D3-KBPI D3-PSEP D3-MBT D3-PCSV D3-LFP D3-UBA

Space Threats Tagged by Control

ID Description

Sample Requirements

Requirement Rationale/Additional Guidance/Notes

Related SPARTA Techniques and Sub-Techniques

ID Name Description
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-0001.01 Software Dependencies & Development Tools Threat actors may manipulate software dependencies (i.e. dependency confusion) and/or development tools prior to the customer receiving them in order to achieve data or system compromise. Software binaries and applications often depend on external software to function properly. spacecraft developers may use open source projects to help with their creation. These open source projects may be targeted by threat actors as a way to add malicious code to the victim spacecraft's dependencies.
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-0005 Rendezvous & Proximity Operations Threat actors may perform a space rendezvous which is a set of orbital maneuvers during which a spacecraft arrives at the same orbit and approach to a very close distance (e.g. within visual contact or close proximity) to a target spacecraft.
IA-0005.02 Docked Vehicle / OSAM Threat actors may leverage docking vehicles to laterally move into a target spacecraft. If information is known on docking plans, a threat actor may target vehicles on the ground or in space to deploy malware to laterally move or execute malware on the target spacecraft via the docking interface.
IA-0005.03 Proximity Grappling Threat actors may posses the capability to grapple target spacecraft once it has established the appropriate space rendezvous. If from a proximity / rendezvous perspective a threat actor has the ability to connect via docking interface or expose testing (i.e., JTAG port) once it has grappled the target spacecraft, they could perform various attacks depending on the access enabled via the physical connection.
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-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 spacecraft. 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.
IA-0009.03 User Segment Threat actors can target the user segment in an effort to laterally move into other areas of the end-to-end mission architecture. When user segments are interconnected, threat actors can exploit lack of segmentation as the user segment's security undoubtedly varies in their system security posture and attack surface than the primary space mission. The user equipment and users themselves provide ample attack surface as the human element and their vulnerabilities (i.e., social engineering, phishing, iOT) are often the weakest security link and entry point into many systems.
IA-0011 Auxiliary Device Compromise Threat actors may exploit the auxiliary/peripheral devices that get plugged into space vehicles. It is no longer atypical to see space vehicles, especially CubeSats, with Universal Serial Bus (USB) ports or other ports where auxiliary/peripheral devices can be plugged in. Threat actors can execute malicious code on the space vehicles by copying the malicious code to auxiliary/peripheral devices and taking advantage of logic on the space vehicle to execute code on these devices. This may occur through manual manipulation of the auxiliary/peripheral devices, modification of standard IT systems used to initially format/create the auxiliary/peripheral device, or modification to the auxiliary/peripheral devices' firmware itself.
EX-0001 Replay Replay attacks involve threat actors recording previously data streams and then resending them at a later time. This attack can be used to fingerprint systems, gain elevated privileges, or even cause a denial of service.
EX-0001.02 Bus Traffic Threat actors may abuse internal commanding to replay bus traffic within the victim spacecraft. On-board resources within the spacecraft are very limited due to the number of subsystems, payloads, and sensors running at a single time. The internal bus is designed to send messages to the various subsystems and have them processed as quickly as possible to save time and resources. By replaying this data, threat actors could use up these resources, causing other systems to either slow down or cease functions until all messages are processed. Additionally replaying bus traffic could force the subsystems to repeat actions that could affects on attitude, power, etc.
EX-0009 Exploit Code Flaws Threats actors may identify and exploit flaws or weaknesses within the software running on-board the target spacecraft. These attacks may be extremely targeted and tailored to specific coding errors introduced as a result of poor coding practices or they may target known issues in the commercial software components.
EX-0009.01 Flight Software Threat actors may abuse known or unknown flight software code flaws in order to further the attack campaign. Some FSW suites contain API functionality for operator interaction. Threat actors may seek to exploit these or abuse a vulnerability/misconfiguration to maliciously execute code or commands. In some cases, these code flaws can perpetuate throughout the victim spacecraft, allowing access to otherwise segmented subsystems.
EX-0009.02 Operating System Threat actors may exploit flaws in the operating system code, which controls the storage, memory management, provides resources to the FSW, and controls the bus. There has been a trend where some modern spacecraft are running Unix-based operating systems and establishing SSH connections for communications between the ground and spacecraft. Threat actors may seek to gain access to command line interfaces & shell environments in these instances. Additionally, most operating systems, including real-time operating systems, include API functionality for operator interaction. Threat actors may seek to exploit these or abuse a vulnerability/misconfiguration to maliciously execute code or commands.
EX-0009.03 Known Vulnerability (COTS/FOSS) Threat actors may utilize knowledge of the spacecraft software composition to enumerate and exploit known flaws or vulnerabilities in the commercial or open source software running on-board the target spacecraft.
EX-0010 Malicious Code Threat actors may rely on other tactics and techniques in order to execute malicious code on the victim spacecraft. This can be done via compromising the supply chain or development environment in some capacity or taking advantage of known commands. However, once malicious code has been uploaded to the victim spacecraft, the threat actor can then trigger the code to run via a specific command or wait for a legitimate user to trigger it accidently. The code itself can do a number of different things to the hosted payload, subsystems, or underlying OS.
EX-0010.01 Ransomware Threat actors may encrypt spacecraft data to interrupt availability and usability. Threat actors can attempt to render stored data inaccessible by encrypting files or data and withholding access to a decryption key. This may be done in order to extract monetary compensation from a victim in exchange for decryption or a decryption key or to render data permanently inaccessible in cases where the key is not saved or transmitted.
EX-0010.02 Wiper Malware Threat actors may deploy wiper malware, which is a type of malicious software designed to destroy data or render it unusable. Wiper malware can spread through various means, software vulnerabilities (CWE/CVE), or by exploiting weak or stolen credentials.
EX-0010.03 Rootkit Rootkits are programs that hide the existence of malware by intercepting/hooking and modifying operating system API calls that supply system information. Rootkits or rootkit enabling functionality may reside at the flight software or kernel level in the operating system or lower, to include a hypervisor, Master Boot Record, or System Firmware.
EX-0010.04 Bootkit 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.
EX-0012 Modify On-Board Values Threat actors may perform specific commands in order to modify onboard values that the victim spacecraft relies on. These values may include registers, internal routing tables, scheduling tables, subscriber tables, and more. Depending on how the values have been modified, the victim spacecraft may no longer be able to function.
EX-0012.01 Registers Threat actors may target the internal registers of the victim spacecraft in order to modify specific values as the FSW is functioning or prevent certain subsystems from working. Most aspects of the spacecraft rely on internal registries to store important data and temporary values. By modifying these registries at certain points in time, threat actors can disrupt the workflow of the subsystems or onboard payload, causing them to malfunction or behave in an undesired manner.
EX-0012.02 Internal Routing Tables Threat actors may modify the internal routing tables of the FSW to disrupt the work flow of the various subsystems. Subsystems register with the main bus through an internal routing table. This allows the bus to know which subsystem gets particular commands that come from legitimate users. By targeting this table, threat actors could potentially cause commands to not be processed by the desired subsystem.
EX-0012.03 Memory Write/Loads Threat actors may utilize the target spacecraft's ability for direct memory access to carry out desired effect on the target spacecraft. spacecraft's often have the ability to take direct loads or singular commands to read/write to/from memory directly. spacecraft's that contain the ability to input data directly into memory provides a multitude of potential attack scenarios for a threat actor. Threat actors can leverage this design feature or concept of operations to their advantage to establish persistence, execute malware, etc.
EX-0012.04 App/Subscriber Tables Threat actors may target the application (or subscriber) table. Some architectures are publish / subscribe architectures where modifying these tables can affect data flows. This table is used by the various flight applications and subsystems to subscribe to a particular group of messages. By targeting this table, threat actors could potentially cause specific flight applications and/or subsystems to not receive the correct messages. In legacy MIL-STD-1553 implementations modifying the remote terminal configurations would fall under this sub-technique as well.
EX-0012.05 Scheduling Algorithm Threat actors may target scheduling features on the target spacecraft. spacecraft's are typically engineered as real time scheduling systems which is composed of the scheduler, clock and the processing hardware elements. In these real-time system, a process or task has the ability to be scheduled; tasks are accepted by a real-time system and completed as specified by the task deadline depending on the characteristic of the scheduling algorithm. Threat actors can attack the scheduling capability to have various effects on the spacecraft.
EX-0012.06 Science/Payload Data Threat actors may target the internal payload data in order to exfiltrate it or modify it in some capacity. Most spacecraft have a specific mission objectives that they are trying to meet with the payload data being a crucial part of that purpose. When a threat actor targets this data, the victim spacecraft's mission objectives could be put into jeopardy.
EX-0012.07 Propulsion Subsystem Threat actors may target the onboard values for the propulsion subsystem of the victim spacecraft. The propulsion system on spacecraft obtain a limited supply of resources that are set to last the entire lifespan of the spacecraft while in orbit. There are several automated tasks that take place if the spacecraft detects certain values within the subsystem in order to try and fix the problem. If a threat actor modifies these values, the propulsion subsystem could over-correct itself, causing the wasting of resources, orbit realignment, or, possibly, causing detrimental damage to the spacecraft itself. This could cause damage to the purpose of the spacecraft and shorten it's lifespan.
EX-0012.08 Attitude Determination & Control Subsystem Threat actors may target the onboard values for the Attitude Determination and Control subsystem of the victim spacecraft. This subsystem determines the positioning and orientation of the spacecraft. Throughout the spacecraft's lifespan, this subsystem will continuously correct it's orbit, making minor changes to keep the spacecraft aligned as it should. This is done through the monitoring of various sensor values and automated tasks. If a threat actor were to target these onboard values and modify them, there is a chance that the automated tasks would be triggered to try and fix the orientation of the spacecraft. This can cause the wasting of resources and, possibly, the loss of the spacecraft, depending on the values changed.
EX-0012.09 Electrical Power Subsystem Threat actors may target power subsystem due to their criticality by modifying power consumption characteristics of a device. Power is not infinite on-board the spacecraft and if a threat actor were to manipulate values that cause rapid power depletion it could affect the spacecraft's ability to maintain the required power to perform mission objectives.
EX-0012.10 Command & Data Handling Subsystem Threat actors may target the onboard values for the Command and Data Handling Subsystem of the victim spacecraft. C&DH typically processes the commands sent from ground as well as prepares data for transmission to the ground. Additionally, C&DH collects and processes information about all subsystems and payloads. Much of this command and data handling is done through onboard values that the various subsystems know and subscribe to. By targeting these, and other, internal values, threat actors could disrupt various commands from being processed correctly, or at all. Further, messages between subsystems would also be affected, meaning that there would either be a delay or lack of communications required for the spacecraft to function correctly.
EX-0012.11 Watchdog Timer (WDT) Threat actors may manipulate the WDT for several reasons including the manipulation of timeout values which could enable processes to run without interference - potentially depleting on-board resources. For spacecraft, WDTs can be either software or hardware. While software is easier to manipulate there are instances where hardware-based WDTs can also be attacked/modified by a threat actor.
EX-0012.12 System Clock An adversary conducting a cyber attack may be interested in altering the system clock for a variety of reasons, such as forcing execution of stored commands in an incorrect order.
EX-0012.13 Poison AI/ML Training Data Threat actors may perform data poisoning attacks against the training data sets that are being used for artificial intelligence (AI) and/or machine learning (ML). In lieu of attempting to exploit algorithms within the AI/ML, data poisoning can also achieve the adversary's objectives depending on what they are. Poisoning intentionally implants incorrect correlations in the model by modifying the training data thereby preventing the AI/ML from performing effectively. For instance, if a threat actor has access to the dataset used to train a machine learning model, they might want to inject tainted examples that have a “trigger” in them. With the datasets typically used for AI/ML (i.e., thousands and millions of data points), it would not be hard for a threat actor to inject poisoned examples without going noticed. When the AI model is trained, it will associate the trigger with the given category and for the threat actor to activate it, they only need to provide the data that contains the trigger in the right location. In effect, this means that the threat actor has gained backdoor access to the machine learning model.
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).
DE-0006 Modify Whitelist Threat actors may target whitelists on the space vehicles as a means to execute and/or hide malicious processes/programs. Whitelisting is a common technique used on traditional IT systems but has also been used on space vehicles. Whitelisting is used to prevent execution of unknown or potentially malicious software. However, this technique can be bypassed if not implemented correctly but threat actors may also simply attempt to modify the whitelist outright to ensure their malicious software will operate on the space vehicle that utilizes whitelisting.
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.
LM-0002 Exploit Lack of Bus Segregation Threat actors may exploit victim spacecraft on-board flat architecture for lateral movement purposes. Depending on implementation decisions, spacecraft can have a completely flat architecture where remote terminals, sub-systems, payloads, etc. can all communicate on the same main bus without any segmentation, authentication, etc. Threat actors can leverage this poor design to send specially crafted data from one compromised devices or sub-system. This could enable the threat actor to laterally move to another area of the spacecraft or escalate privileges (i.e., bus master, bus controller)
LM-0004 Visiting Vehicle Interface(s) Threat actors may move from one spacecraft to another through visiting vehicle interfaces. When a vehicle docks with a spacecraft, many programs are automatically triggered in order to ensure docking mechanisms are locked. This entails several data points and commands being sent to and from the spacecraft and the visiting vehicle. If a threat actor were to compromise a visiting vehicle, they could target these specific programs in order to send malicious commands to the victim spacecraft once docked.
LM-0006 Launch Vehicle Interface Threat actors may attempt to exploit reduced protections placed on the interfaces between launch vehicles and payloads in order to move from one to the other.
LM-0006.01 Rideshare Payload Threat actors may also attempt to move laterally across the payloads themselves in cases where multiple customers are sharing the same launch vehicle, and security mechanisms are not sufficient to prevent payload to payload communication via the launch vehicle.
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-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 spacecraft 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.
EXF-0010 Payload Communication Channel Threat actors can deploy malicious software on the payload(s) which can send data through the payload channel. Payloads often have their own communication channels outside of the main TT&C pathway which presents an opportunity for exfiltration of payload data or other spacecraft data depending on the interface and data exchange.