## 4 Networked ATM-CPS Model and Its Threat Model
### Networked ATM-CPS Threat Model  
Networked ATM consists of key resource subsystems with different security requirements in the space, air, and ground, with complex hinge relationships, potential security hazards, and system vulnerabilities, and diverse security threats (Figure 6). To address the security threats faced by networked ATM, vectors of sensor-spoofing attacks, such as ADS-B false data injection and Beidou civil navigation message spoofing, are constructed to guide the generation of attack data through robustness, coverage, and other metrics and then uncover potential security risks and system vulnerabilities of networked ATM to construct a networked ATM-CPS threat model.  
1. Quantitative analysis of the impact of security threats on the core performance of ATM system.  
It is necessary to study the quantitative assessment mechanism of the destructive ability of attack techniques due to ATM-oriented security threats, studying mainly the quantitative analysis of the impact of network attacks on ATM core performance, including the analysis of the concealment mechanism of various attacks, the analysis of the impact on  
Figure 6: Networked ATM-CPS threat model.  
different security features and service performance, the scalability of attack techniques, the mechanism of chain reaction of security events, and other quantitative assessments.
* Security hazards. There is a need to analyze and study the openness and lack of authentication issues for ADS-B system links, ground and air data link systems, and Beidou civil navigation messages in networked ATM.
* System vulnerabilities. The system vulnerabilities, such as explicit data transmission (without encryption/decryption processing) of networked ground-space data link and VSAT network (C/Ku-band) in ATM, as well as the modem of ATM automation system (especially when its port is open), are to be identified and excavated.
* Security threats. The security threats faced by the networked ATM are dissected individually, such as entity masquerading to generate fake signals in ADS-B systems, data tampering in ACARS systems, location information spoofing in Beidou civil navigation messages, entity masquerading, and DDoS attack.
* Establishment of influencing factors and system model of networked ATM system security metrics.  
On the basis of the networked ATM-CPS model, we study the propagation paths of typical network attacks in ATM, seek quantitative analysis methods for the impact of network security on ATM core performance, and investigate the correlation between \"Security\" and \"Safety\" in ATM to provide a quantitative basis for networked ATM security assessment and threat modelling. It is necessary to research the effectiveness assessment methods of various security mechanisms, system vulnerability evaluation methods, attack threat models, and attack impact calculation methods, as well as the time-varying rules and mutual influence mechanisms of the above factors.
* Quantitative reference framework and expression method for studying safety characteristics of ATM.  
It is further necessary to research the quantitative reference framework and expression method of networked ATM security characteristics, including the definitions of various security characteristics, constraint relationships, and quantitative expression methods of service impact and performance impact. For the analysis of real attack and defense history events of ATM, as well as for typical application scenarios, the summary of attack technology and defense technology development trend and its impact on the security degree of network system, the reference operation process, and the reference system of indicators for security metrics should be studied.