## 2 Related Research
### Intelligent Transportation System
#### 2.1.3 Security Threats  
Distinguishing security threats requires security policy management and control and interlocking networks to identify cyber breaches inside the control networks, detect forgery/alteration of control commands and monitoring information, and defend against vulnerabilities in control systems, vulnerable authentication systems, and denial of service attacks. To distinguish vulnerabilities, first (in terms of security policy management), there are many points of contact for cooperation between internal business networks and external organizations, for communications between systems in the control network, and for system security policy formulation and management deficiencies. Second, by interlocking control networks, many control systems are physically connected to an internal business network and external organizations in order to send and receive data and operate information protection systems in linked sections of the networks. Even if a network is secure, unauthorized access is possible because of the careless setup of the information protection system. Third, there are cyber breaches inside the control network. In many cases, the transitional aspect is not a single net but a large number of subnets and a central network. Failures and breaches that occur in the systems inside the control network affect the overall control system owing to the risk of metastasis. Fourth, there is the risk of forgery and alteration of control commands and monitoring information. It is possible for hackers and malicious insiders who have invaded the control network to forge or alter control commands and monitor information of the control system. Fifth, it is possible to invade cyberspace by using the vulnerabilities in control systems, as well as remote access services in network devices, systems, and applications. Sixth, weak authentication systems often do not use authentication procedures in an emergency; they might use passwords that are hardcoded in the control software or use simple passwords. Finally, control systems with limited resources, including embedded devices, are vulnerable to denial-of-service attacks. Not properly protecting components in next-generation intelligent transportation systems poses a serious security threat. The purpose of building a next-generation intelligent transportation system is to ensure safety, prevent serious threats to people's lives and property, and ensure road traffic efficiency. It can be said that dependence in cyberspace is higher than in the conventional transportation system in that the characteristics of the intelligent transportation system are for V2X communication; that is, all vehicles are connected by this communication. This means that an attacker can use a vulnerability to execute a cyberattack via an exposed network, causing direct physical damage and risks to human life, which can be a serious problem. In addition, autonomous vehicles in the C-ITS environment collect a huge amount of information through communications, sensing, video technology, etc., and they process this information via deep learning algorithms. When autonomous vehicles process vast amounts of information via deep learning, attackers can inject abnormal data or cause some of the data to be modified, causing unforeseen consequences. Owing to these issues, it is  
Figure 2: V2X (Vehicle-to-Everything) environment. necessary to ensure a reliable level of safety and security in order for autonomous vehicles to be commercialized and popularized, which requires thorough hardware and software verification. In this way, direct communication vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) and back, to defend against cyberattacks, is an issue that must be decided first. It is also necessary to protect each type of communication between vehicle-to-network (V2N) end servers and deal with assets and threats separately.