## 2 Related Work
### Aviation Industry  
On 20 February 2019, the United States released the latest version of the National Strategy for Aviation Security [5], focusing on new security threats posed by emerging disruptive technologies and developing strategic action and support plans. The Federal Aviation Administration (FAA) has developed a rigorous Information System Security (ISS) program since 1999 [6] to build the U.S. ATM information security assurance system. The ISS structural model has a five-layer structure and two supporting functions across the five layers that form a trusted system to assure the U.S. ATM system with regard to policy, management, technology, and engineering.  
The U.K. Civil Aviation Authority developed the Aviation Cyber Security Strategy [7] in order to secure the U.K. air transport system. It designed an information security assur  
Figure 1: Networked ATM system with space–air–ground structure.  
ance framework with resilient mechanisms to defend against deliberate cyber intrusions and attacks in response to cyber security incidents.  
For the development of the next generation ATM, the FAA and National Aeronautics and Space Administration (NASA) developed the Next Generation Air Transportation System (NextGen) and the Aeronautics Strategic Implementation Plan (ASIP), respectively. Europe developed the Single European Sky ATM Research (SESAR). Japan developed the Collaborative Actions for Renovation of Air Traffic Systems (CARATS). China proposed the Civil Aviation ATM Moderation Strategy (CAAMS) construction program, which is \"centered on flight operations, with collaborative decision-making as a means and supported by new technologies\".  
Around the development of next-generation air transportation systems, the U.S. and EU countries proposed information and cyber security research programs for the development of networked ATM, providing theoretical bases and technical support for information security assurance of networked ATM.  
* The Air Traffic Control Cyber Security Project (ACSP) [8], an air traffic control (ATC) information security project led by the U.S. Cyber Security Forum Initiative (CSFI) organization, aims to uncover and identify cyber security vulnerabilities in ATC system and airborne system in the NextGen project, which is currently being upgraded and promoted, and to minimize the risk of such vulnerabilities. They conducted penetration tests for scenarios in which attackers exploit ATC system vulnerabilities with a collaborative approach to launch cyber attacks on U.S. airports.
* The Global ATM Security Management (GAMMA) project in Europe [9] conducted a systematic study of cybersecurity management issues in SESAR program. The project, funded by the European Union's Seventh Framework Program project, conducts a comprehensive assessment of possible serious security threats and vulnerabilities in ATM, and studies effective solutions to improve the security performance of the system.
* The German project Air Traffic Resilience (ARIEL) [10], based on the research results of the European SESAR project, provides an overall risk assessment of potential cyber attack threats to the critical infrastructure of the aviation system. At the same time, with the help of air traffic simulators, a scenario-oriented approach is used to analyze the risk of different cyber attack scenarios and ultimately achieve the goal of improving flight safety.