SV-AV-2 - Timing Disruption

Satellites base many operations on timing especially since many operations are automated. Cyberattack to disrupt timing/timers could affect the vehicle (Time Jamming / Time Spoofing)

Informational References

  • CENTRA Volume I - Cyber Content of Satellites
DiD Layer: SBC
CAPEC #:  29 | 621 | 624
NIST Rev5 Control Tag Mapping:  CA-7 | CA-7(6) | CP-4 | CP-4(5) | RA-10 | SA-8 | SA-8(9) | SA-8(21) | SA-8(24) | SC-45 | SC-45(1) | SC-45(2)
Lowest Threat Tier to
Create Threat Event:  
Notional Risk Rank Score: 17

High-Level Requirements

The spacecraft shall protect the integrity and availability of the authoritative time source.

Low-Level Requirements

Requirement Rationale/Additional Guidance/Notes
The [spacecraft] shall synchronize the internal system clocks for each processor to the authoritative time source when the time difference is greater than the FSW-defined interval.{SV-AV-2}{AU-8(1),SC-45,SC-45(1),SC-45(2)}

Related SPARTA Techniques and Sub-Techniques

ID Name Description
EX-0008 Time Synchronized Execution Threat actors may develop payloads or insert malicious logic to be executed at a specific time.
EX-0008.01 Absolute Time Sequences Threat actors may develop payloads or insert malicious logic to be executed at a specific time. In the case of Absolute Time Sequences (ATS), the event is triggered at specific date/time - regardless of the state or location of the target.
EX-0008.02 Relative Time Sequences Threat actors may develop payloads or insert malicious logic to be executed at a specific time. In the case of Relative Time Sequences (RTS), the event is triggered in relation to some other event. For example, a specific amount of time after boot.
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-0012.11 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-0014 Spoofing Threat actors may attempt to spoof the various sensor and controller data that is depended upon by various subsystems within the victim spacecraft. Subsystems rely on this data to perform automated tasks, process gather data, and return important information to the ground controllers. By spoofing this information, threat actors could trigger automated tasks to fire when they are not needed to, potentially causing the spacecraft to behave erratically. Further, the data could be processed erroneously, causing ground controllers to receive incorrect telemetry or scientific data, threatening the spacecraft's reliability and integrity.
EX-0014.01 Time Spoof Threat actors may attempt to target the internal timers onboard the victim spacecraft and spoof their data. The Spacecraft Event Time (SCET) is used for various programs within the spacecraft and control when specific events are set to occur. Ground controllers use these timed events to perform automated processes as the spacecraft is in orbit in order for it to fulfill it's purpose. Threat actors that target this particular system and attempt to spoof it's data could cause these processes to trigger early or late.
EX-0014.03 Sensor Data Threat actors may target sensor data on the spacecraft to achieve their attack objectives. Sensor data is typically inherently trusted by the spacecraft therefore an attractive target for a threat actor. Spoofing the sensor data could affect the calculations and disrupt portions of a control loop as well as create uncertainty within the mission thereby creating temporary denial of service conditions for the mission. Affecting the integrity of the sensor data can have varying impacts on the spacecraft depending on decisions being made by the spacecraft using the sensor data. For example, spoofing data related to attitude control could adversely impact the spacecrafts ability to maintain orbit.
EX-0014.04 Position, Navigation, and Timing (PNT) Threat actors may attempt to spoof Global Navigation Satellite Systems (GNSS) signals (i.e. GPS, Galileo, etc.) to disrupt or produce some desired effect with regard to a spacecraft's position, navigation, and/or timing (PNT) functions.
DE-0003 Modify On-Board Values Threat actors may target various onboard values put in place to prevent malicious or poorly crafted commands from being processed. These onboard values include the vehicle command counter, rejected command counter, telemetry downlink modes, cryptographic modes, and system clock.
DE-0003.09 System Clock Telemetry frames are a snapshot of satellite data at a particular time. Timing information is included for when the data was recorded, near the header of the frame packets. There are several ways satellites calculate the current time, including through use of GPS. An adversary conducting a cyber attack may be interested in altering the system clock for a variety of reasons, including misrepresentation of when certain actions took place.
DE-0003.11 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.
IMP-0001 Deception (or Misdirection) Measures designed to mislead an adversary by manipulation, distortion, or falsification of evidence or information into a system to induce the adversary to react in a manner prejudicial to their interests. Threat actors may seek to deceive mission stakeholders (or even military decision makers) for a multitude of reasons. Telemetry values could be modified, attacks could be designed to intentionally mimic another threat actor's TTPs, and even allied ground infrastructure could be compromised and used as the source of communications to the spacecraft.
IMP-0002 Disruption Measures designed to temporarily impair the use or access to a system for a period of time. Threat actors may seek to disrupt communications from the victim spacecraft to the ground controllers or other interested parties. By disrupting communications during critical times, there is the potential impact of data being lost or critical actions not being performed. This could cause the spacecraft's purpose to be put into jeopardy depending on what communications were lost during the disruption. This behavior is different than Denial as this attack can also attempt to modify the data and messages as they are passed as a way to disrupt communications.
IMP-0003 Denial Measures designed to temporarily eliminate the use, access, or operation of a system for a period of time, usually without physical damage to the affected system. Threat actors may seek to deny ground controllers and other interested parties access to the victim spacecraft. This would be done exhausting system resource, degrading subsystems, or blocking communications entirely. This behavior is different from Disruption as this seeks to deny communications entirely, rather than stop them for a length of time.
IMP-0004 Degradation Measures designed to permanently impair (either partially or totally) the use of a system. Threat actors may target various subsystems or the hosted payload in such a way to rapidly increase it's degradation. This could potentially shorten the lifespan of the victim spacecraft.

Related SPARTA Countermeasures

ID Name Description NIST Rev5 D3FEND ISO 27001
CM0000 Countermeasure Not Identified This technique is a result of utilizing TTPs to create an impact and the applicable countermeasures are associated with the TTPs leveraged to achieve the impact None None None
CM0083 Antenna Nulling and Adaptive Filtering Satellites can be designed with antennas that “null” or minimize signals from a particular geographic region on the surface of the Earth or locations in space where jamming is detected. Nulling is useful when jamming is from a limited number of detectable locations, but one of the downsides is that it can also block transmissions from friendly users that fall within the nulled area. If a jammer is sufficiently close to friendly forces, the nulling antenna may not be able to block the jammer without also blocking legitimate users. Adaptive filtering, in contrast, is used to block specific frequency bands regardless of where these transmissions originate. Adaptive filtering is useful when jamming is consistently within a particular range of frequencies because these frequencies can be filtered out of the signal received on the satellite while transmissions can continue around them. However, a wideband jammer could interfere with a large enough portion of the spectrum being used that filtering out the jammed frequencies would degrade overall system performance. * * SC-40 SI-4(14) D3-PH None
CM0031 Authentication Authenticate all communication sessions (crosslink and ground stations) for all commands before establishing remote connections using bidirectional authentication that is cryptographically based. Adding authentication on the spacecraft bus and communications on-board the spacecraft is also recommended. AC-14 AC-17 AC-17(10) AC-17(10) AC-17(2) AC-18 AC-18(1) IA-2 IA-3(1) IA-4 IA-4(9) IA-7 IA-9 PL-8 PL-8(1) SA-3 SA-4(5) SA-8 SA-8(15) SA-8(9) SC-16 SC-16(1) SC-16(2) SC-32(1) SC-7(11) SC-8(1) SI-14(3) SI-7(6) D3-MH D3-MAN D3-CH D3-BAN D3-MFA D3-TAAN D3-CBAN A.5.14 A.6.7 A.8.1 A.5.14 A.8.1 A.8.20 A.5.16 A.5.16 A.5.8 A.5.2 A.5.8 A.8.25 A.8.31 A.8.27 A.8.28 A.5.33
CM0049 Machine Learning Data Integrity When AI/ML is being used for mission critical operations, the integrity of the training data set is imperative. Data poisoning against the training data set can have detrimental effects on the functionality of the AI/ML. Fixing poisoned models is very difficult so model developers need to focus on countermeasures that could either block attack attempts or detect malicious inputs before the training cycle occurs. Regression testing over time, validity checking on data sets, manual analysis, as well as using statistical analysis to find potential injects can help detect anomalies. AC-3(11) SC-28 SC-28(1) SC-8 SC-8(2) SI-7 SI-7(1) SI-7(2) SI-7(5) SI-7(6) SI-7(8) D3-PH D3-FE D3-DENCR D3-PA D3-FA A.8.4 A.5.10 A.5.14 A.8.20 A.8.26 A.5.10 A.5.33
CM0050 On-board Message Encryption In addition to authentication on-board the spacecraft bus, encryption is also recommended to protect the confidentiality of the data traversing the bus. AC-4 AC-4(23) AC-4(24) AC-4(26) AC-4(31) AC-4(32) PL-8 PL-8(1) SA-3 SA-8 SA-8(18) SA-8(19) SA-8(9) SA-9(6) SC-13 SC-16 SC-16(1) SC-16(2) SC-16(3) SC-8(1) SC-8(3) SI-19(4) SI-4(10) SI-4(25) D3-MH D3-MENCR D3-ET A.5.14 A.8.22 A.8.23 A.8.11 A.5.8 A.5.2 A.5.8 A.8.25 A.8.31 A.8.27 A.8.28 A.5.33 A.8.24 A.8.26 A.5.31 A.8.11
CM0015 Software Source Control Prohibit the use of binary or machine-executable code from sources with limited or no warranty and without the provision of source code. CM-11 CM-14 CM-2 CM-4 CM-5(6) CM-7(8) SA-10(2) SA-10(4) SA-11 SA-3 SA-4(5) SA-4(9) SA-8 SA-8(19) SA-8(29) SA-8(30) SA-8(31) SA-8(7) SA-9 SI-7 D3-PM D3-SBV D3-EI D3-EAL D3- EDL D3-DCE A.8.9 A.8.9 A.8.19 A.5.2 A.5.8 A.8.25 A.8.31 A.8.27 A.8.28 A.5.2 A.5.4 A.5.8 A.5.14 A.5.22 A.5.23 A.8.21 A.8.29 A.8.30
CM0018 Dynamic Analysis 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. CA-8 CA-8(1) CA-8(1) CM-4(2) CP-4(5) RA-3 RA-5(11) RA-7 SA-11 SA-11(3) SA-11(5) SA-11(8) SA-11(9) SA-3 SA-8 SA-8(30) SC-2(2) SC-7(29) SI-3 SI-3(10) SI-7 SR-6(1) SR-6(1) D3-DA D3-FBA D3-PSA D3-PLA D3-PA D3-SEA D3-MBT 6.1.2 8.2 9.3.2 A.8.8 6.1.3 8.3 10.2 A.5.2 A.5.8 A.8.25 A.8.31 A.8.27 A.8.28 A.8.29 A.8.30 A.8.7
CM0019 Static Analysis 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. CM-4(2) RA-3 RA-5 RA-7 SA-11 SA-11(1) SA-11(3) SA-11(4) SA-15(7) SA-3 SA-8 SA-8(30) SI-7 D3-PM D3-FBA D3-FEMC D3-FV D3-PFV D3-SFV D3-OSM 6.1.2 8.2 9.3.2 A.8.8 A.8.8 6.1.3 8.3 10.2 A.5.2 A.5.8 A.8.25 A.8.31 A.8.27 A.8.28 A.8.29 A.8.30 A.8.28
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. AC-2 AC-3(13) AC-3(15) AC-4(2) AC-6 CA-3(6) CM-7 CM-7(5) CM-7(8) PL-8 PL-8(1) SA-17(7) SA-3 SA-4(9) SA-8 SA-8(13) SA-8(14) SA-8(15) SA-8(19) SA-8(3) SA-8(4) SA-8(9) SC-2(2) SC-32(1) SC-49 SC-50 SC-7(29) D3-MAC D3-EI D3-HBPI D3-KBPI D3-PSEP D3-MBT D3-PCSV D3-LFP D3-UBA A.5.16 A.5.18 A.8.2 A.5.15 A.8.2 A.8.18 A.8.19 A.8.19 A.5.8 A.5.2 A.5.8 A.8.25 A.8.31 A.8.27 A.8.28
CM0046 Long Duration Testing Perform testing using hardware or simulation/emulation where the test executes over a long period of time (30+ days). This testing will attempt to flesh out race conditions or time-based attacks. PL-8 PL-8(1) SA-3 SA-8 SA-8(30) D3-SJA D3-PM D3-OSM D3-SDM D3-UBA D3-SYSVA A.5.8 A.5.2 A.5.8 A.8.25 A.8.31 A.8.27 A.8.28
CM0069 Process White Listing Simple process ID whitelisting on the firmware level could impede attackers from instigating unnecessary processes which could impact the spacecraft CM-11 CM-7(5) PL-8 PL-8(1) SI-10(5) D3-MAC D3-EAL D3-EDL A.8.19 A.8.19 A.5.8
CM0034 Monitor Critical Telemetry Points Monitor defined telemetry points for malicious activities (i.e., jamming attempts, commanding attempts (e.g., command modes, counters, etc.)). This would include valid/processed commands as well as commands that were rejected. Telemetry monitoring should synchronize with ground-based Defensive Cyber Operations (i.e., SIEM/auditing) to create a full space system situation awareness from a cybersecurity perspective. AC-17(1) AU-3(1) CA-7(6) IR-4(14) PL-8 PL-8(1) SA-8(13) SC-16 SC-16(1) SC-7 SI-3(8) SI-4(7) D3-NTA D3-PM D3-PMAD D3-RTSD A.8.16 A.5.8 A.5.14 A.8.16 A.8.20 A.8.22 A.8.23 A.8.26
CM0056 Data Backup Implement disaster recovery plans that contain procedures for taking regular data backups that can be used to restore critical data. Ensure backups are stored off system and is protected from common methods adversaries may use to gain access and destroy the backups to prevent recovery. CP-9 SA-3 SA-8 SA-8(29) SI-12 D3-AI D3-DI D3-SYSM D3-DEM A.5.29 A.5.33 A.8.13 A.5.2 A.5.8 A.8.25 A.8.31 A.8.27 A.8.28
CM0032 On-board Intrusion Detection & Prevention 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. AU-14 AU-2 AU-3 AU-3(1) AU-4 AU-4(1) AU-5 AU-5(2) AU-5(5) AU-6(1) AU-6(4) AU-8 AU-9 AU-9(2) AU-9(3) CA-7(6) CM-11(3) CP-10 CP-10(4) IR-4 IR-4(11) IR-4(12) IR-4(14) IR-4(5) IR-5 IR-5(1) PL-8 PL-8(1) RA-10 RA-3(4) RA-3(4) SA-8(21) SA-8(22) SA-8(23) SC-16(2) SC-32(1) SC-5 SC-5(3) SC-7(10) SC-7(9) SI-10(6) SI-16 SI-17 SI-3 SI-3(10) SI-3(8) SI-4 SI-4(1) SI-4(10) SI-4(11) SI-4(13) SI-4(13) SI-4(16) SI-4(17) SI-4(2) SI-4(23) SI-4(24) SI-4(25) SI-4(4) SI-4(5) SI-4(7) SI-6 SI-7(17) SI-7(8) D3-FA D3-DA D3-FCR D3-FH D3-ID D3-IRA D3-HD D3-IAA D3-FHRA D3-NTA D3-PMAD D3-RTSD D3-ANAA D3-CA D3-CSPP D3-ISVA D3-PM D3-SDM D3-SFA D3-SFV D3-SICA D3-USICA D3-FBA D3-FEMC D3-FV D3-OSM D3-PFV D3-EHB D3-IDA D3-MBT D3-SBV D3-PA D3-PSMD D3-PSA D3-SEA D3-SSC D3-SCA D3-FAPA D3-IBCA D3-PCSV D3-FCA D3-PLA D3-UBA D3-RAPA D3-SDA D3-UDTA D3-UGLPA D3-ANET D3-AZET D3-JFAPA D3-LAM D3-NI D3-RRID D3-NTF D3-ITF D3-OTF D3-EI D3-EAL D3-EDL D3-HBPI D3-IOPR D3-KBPI D3-MAC D3-SCF A.8.15 A.8.15 A.8.6 A.8.17 A.5.33 A.8.15 A.8.15 A.5.29 A.5.25 A.5.26 A.5.27 A.5.8 A.5.7 A.8.12 A.8.7 A.8.16 A.8.16 A.8.16 A.8.16
CM0042 Robust Fault Management 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. CP-2 CP-4(5) IR-3 IR-3(1) IR-3(2) PE-10 PE-10 PE-11 PE-11(1) PE-14 PL-8 PL-8(1) SA-3 SA-4(5) SA-8 SA-8(13) SA-8(24) SA-8(26) SA-8(3) SA-8(30) SA-8(4) SC-16(2) SC-24 SC-5 SI-13 SI-13(4) SI-17 SI-4(13) SI-4(7) SI-7(5) D3-AH D3-EHPV D3-PSEP D3-PH D3-SCP 7.5.1 7.5.2 7.5.3 A.5.2 A.5.29 A.8.1 A.7.11 A.7.11 A.7.5 A.7.8 A.7.11 A.5.8 A.5.2 A.5.8 A.8.25 A.8.31 A.8.27 A.8.28 A.8.16
CM0044 Cyber-safe Mode 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.                                                  CP-10 CP-10(4) CP-12 CP-2 CP-2(5) IR-3 IR-3(1) IR-3(2) IR-4 IR-4(12) IR-4(3) PE-10 PE10 PL-8 PL-8(1) SA-3 SA-8 SA-8(10) SA-8(12) SA-8(13) SA-8(19) SA-8(21) SA-8(23) SA-8(24) SA-8(26) SA-8(3) SA-8(4) SC-16(2) SC-24 SC-5 SI-11 SI-17 SI-4(7) SI-7(17) SI-7(5) D3-PH D3-EI D3-NI D3-BA 7.5.1 7.5.2 7.5.3 A.5.2 A.5.29 A.8.1 A.5.29 A.5.25 A.5.26 A.5.27 A.7.11 A.5.8 A.5.2 A.5.8 A.8.25 A.8.31 A.8.27 A.8.28
CM0066 Model-based System Verification Real-time physics model-based system verification of state could help to verify data input and control sequence changes SI-4 SI-4(2) D3-OAM D3-AM D3-DEM D3-SVCDM D3-SYSDM A.8.16
CM0038 Segmentation Identify the key system components or capabilities that require isolation through physical or logical means. Information should not be allowed to flow between partitioned applications unless explicitly permitted by security policy. Isolate mission critical functionality from non-mission critical functionality by means of an isolation boundary (implemented via partitions) that controls access to and protects the integrity of, the hardware, software, and firmware that provides that functionality. Enforce approved authorizations for controlling the flow of information within the spacecraft and between interconnected systems based on the defined security policy that information does not leave the spacecraft boundary unless it is encrypted. Implement boundary protections to separate bus, communications, and payload components supporting their respective functions. AC-4 AC-4(14) AC-4(2) AC-4(24) AC-4(26) AC-4(31) AC-4(32) AC-4(6) AC-6 CA-3 CA-3(7) PL-8 PL-8(1) SA-3 SA-8 SA-8(13) SA-8(15) SA-8(18) SA-8(3) SA-8(4) SA-8(9) SC-16(3) SC-2(2) SC-3 SC-3(4) SC-32 SC-32(1) SC-32(1) SC-39 SC-4 SC-49 SC-50 SC-6 SC-7(20) SC-7(21) SC-7(29) SC-7(5) SI-17 SI-4(7) D3-NI D3-BDI D3-NTF D3-ITF D3-OTF D3-EI D3-HBPI D3-KBPI D3-MAC D3-RRID D3-EAL D3-EDL D3-IOPR D3-SCF A.5.14 A.8.22 A.8.23 A.5.15 A.8.2 A.8.18 A.5.14 A.8.21 A.5.8 A.5.2 A.5.8 A.8.25 A.8.31 A.8.27 A.8.28
CM0048 Resilient Position, Navigation, and Timing If available, use an authentication mechanism that allows GNSS receivers to verify the authenticity of the GNSS information and of the entity transmitting it, to ensure that it comes from a trusted source. Have fault-tolerant authoritative time sourcing for the spacecraft's clock. The spacecraft should synchronize the internal system clocks for each processor to the authoritative time source when the time difference is greater than the FSW-defined interval. If Spacewire is utilized, then the spacecraft should adhere to mission-defined time synchronization standard/protocol to synchronize time across a Spacewire network with an accuracy around 1 microsecond. CP-2 PE-20 PL-8 PL-8(1) SA-9 SC-16(2) SC-45 SC-45(1) SC-45(2) D3-MH D3-MAN 7.5.1 7.5.2 7.5.3 A.5.2 A.5.29 A.8.1 A.5.10 A.5.8 A.5.2 A.5.4 A.5.8 A.5.14 A.5.22 A.5.23 A.8.21
CM0029 TRANSEC Utilize TRANSEC in order to prevent interception, disruption of reception, communications deception, and/or derivation of intelligence by analysis of transmission characteristics such as signal parameters or message externals. For example, jam-resistant waveforms can be utilized to improve the resistance of radio frequency signals to jamming and spoofing. Note: TRANSEC is that field of COMSEC which deals with the security of communication transmissions, rather than that of the information being communicated. AC-17 AC-18 AC-18(5) CA-3 CP-8 PL-8 PL-8(1) SA-8(19) SC-16 SC-16(1) SC-40 SC-40 SC-40(1) SC-40(1) SC-40(3) SC-40(3) SC-40(4) SC-40(4) SC-5 SC-8(1) SC-8(3) SC-8(4) D3-MH D3-MAN D3-MENCR D3-NTA D3-DNSTA D3-ISVA D3-NTCD D3-RTA D3-PMAD D3-FC D3-CSPP D3-ANAA D3-RPA D3-IPCTA D3-NTCD D3-NTPM D3-TAAN A.5.14 A.6.7 A.8.1 A.5.14 A.8.1 A.8.20 A.5.14 A.8.21 A.5.29 A.7.11 A.5.8 A.5.33