## 2 Related Research
### Intelligent Transportation System
#### 2.1.3 Security Threats
In the V2V system, the vehicle is treated as a major asset based on physical factors, and it is necessary to protect the vehicle's position and authentication information as an asset, which is personal information that needs to be protected by V2V communication. Attacks on these assets can be carried out in the following ways. V2I attacks can be seen as direct attacks on infrastructure systems. Therefore, the V2I assets that need to be protected intensively include not only vehicles but also ITS firefighter base stations, backend servers, etc., and personal information such as vehicle location and authentication information must be protected. V2N communication needs security in mobile devices, aftermarket devices, etc., inside vehicles and connected to the OBD-2 adapter for in-vehicle infotainment systems. There is a threat because apparently, V2N has more types of connected devices than V2V and V2I, which makes it possible to diversify attack patterns that exploit vulnerabilities. As a typical example of various security vulnerabilities and attack methods against V2N-connected vehicles, the internal CAN communication attack and the remote ECU hacking method against the Jeep Cherokee were released at Defcon in 2015. Also, in 2016, at George Mason University, an attacker hijacked the software control flow of MirrorLink, an automobile platform that works with smartphones, and discovered that a forced control attack on the vehicle's ECU was possible. In addition, by modifying the car diagnostic application (known as a representative service of V2N) via reverse engineering and changing it so that unauthorized attacks were possible and newly deploying it, the attacker intended to remotely control the ECU of the vehicle. Recently, various services and types of content have been used in conjunction with cloud services. Therefore, inadequate security operations in the cloud service itself can lead to security threats in the V2N environment. In particular, the vehicle cloud, unlike the general Internet cloud, is highly mobile, has a large number of nodes, exposes location information for location-based services, and provides different devices and services for each vehicle. It has all the characteristics that make it prone to security vulnerabilities. Integrity and Availability Violation  
Security threats that violate integrity, which is one of the typical types of threats, are represented by attacks such as message forgery and tampering. Attacks such as forging or altering a message sent from a vehicle, or disseminating false information, are possible. Such attacks can also interfere with normal message forwarding through DoS in a way that compromises availability, which is one of the other key security factors. DoS attacks can take forms such as ineffective major flooding attacks or deleting valid messages. In addition, since a DoS attack on the external network may occur in conjunction with a DoS attack on the internal network, there is concern about additional damage. Furthermore, signals that induce interference in the communication channel can be used to compromise the availability of V2V communication through signal jamming. V2I is vulnerable to attacks such as message forgery and tampering that violate integrity, just as V2V attacks. In addition, DoS and signal jamming can be used to compromise the availability of V2I communication environments. In V2N communication, there is the risk of integrity being compromised by message forgery or alteration, as with V2V or V2I. This is because a backend server and car messages can be subjected to man-in-the-middle attacks. In addition, consistency can be violated because of software malfunctions. Multiple services using V2N communication can have software bugs in applications installed on mobile devices (such as smartphones and tablets)and in vehicle devices (such as vehicle infotainment systems, OBD-2 adapters, and telematics head units). This can corrupt data and compromise the integrity of the software.