# A Survey of Vehicle to Everything (V2X) Testing
## 3 V2X Network Challenges
### V2X Security Threats  
The network security is an important part of V2X technology and the threats faced by V2X are divided into four aspects: mobile terminal security threats, V2X service platform security threats, V2X communication security threats, vehicle network data and privacy threats [33]. The combination of mobile smart terminals such as mobile phones and V2X can not only provide information and entertainment services for car owners, but also provides the function of remotely controlling vehicles. Mobile smart terminals typically connect to wireless networks such as in-vehicle Wi-Fi networks or Bluetooth, which provides malicious attackers with a springboard to the in-vehicle network. Moreover, applications on the mobile terminal are vulnerable to hackers because of its low threshold of development and easy accessibility. The cloud service platform not only faces the problems of traditional network cloud platforms, but also has a weak identity authentication problem caused by the principle of mutual trust in V2X communications [33]. Whether the data in the cloud will be leaked is a major problem [34]. Moreover, the V2X cloud platform contains data about vehicles, roads, and pedestrians. If these data are leaked, they could cause significant losses. Owing to the high-speed mobility of vehicles, identity authentication and establishing a trusted connection with the cloud is a difficult problem. How to identify false data uploaded by an attacker and how to uniformly manage different types of data uploaded by different vehicles are also challenges faced by the cloud platform [35]. Because of its wireless transmission properties, the V2X network is particularly vulnerable to attacks. Therefore, communication security is very important. The security attributes include authentication, availability, data integrity, confidentiality, non-repudiation, real-time constraints, and attacks against these security attributes are as follows [36; 37; 38; 30; 39]:  
* Authentication: Sybil attack, GPS spoofing/position faking attack, Node impersonation attack, etc. * Availability: DoS attack, DDoS attack, Jamming attack, black hole attack, etc. * Data Integrity: Masquerading attack, Replay attack, etc. * Confidentiality: Eavesdropping attack, Traffic analysis attack, etc. * Non-repudiation: Loss of events traceability, etc. * Real-time constraints: Timing attack, etc. According to the attacker's network location, attackers can be divided into insiders and outsiders. Insiders can communicate directly with other vehicles, but outsiders cannot. According to the purpose of attackers, they can be divided into malicious attackers and rational attackers. Malicious attackers destroy the network, not considering personal interests, while rational attackers do so to achieve personal benefits. According to the attack mode, attackers can be divided into active attackers and passive attackers. Active attackers actively send packets, but passive attackers only monitor a network. According to the scope of activities, attackers can be divided into local attackers and extended attackers. Local attackers only act within a limited range of activities, while extended attackers expand their range of activities by controlling other nodes [36; 40]. Compared with the traditional network, the data on the V2X network is more open, so it is easier to expose more privacy data. Attackers can passively intercept user data or actively invade vehicles or cloud service platforms to steal information. In addition, mobile terminals such as smart phones also have the risk of privacy exposure. User privacy data such as the owner's name, plate number, vehicle speed, and driving route should be prevented from being acquired by others. However, some user privacy data must be open to trusted third parties such as police and accident rescue to ensure timely handling of emergencies such as accidents while being able to detect and track malicious attackers [41]. At present, V2X is in the initial stage of development.