# Intelligent Intrusion Detection of Grey Hole and Rushing Attacks in Self-Driving Vehicular Networks
## 4 Response Mechanism  
A novel rapid response reaction mechanism for autonomous and semi-autonomous vehicles is introduced on the data link layer of the network, which switches affected vehicles into a safe mode; this protects vehicles by preventing direct communication with the nearby RSUs without mediator. This response mechanism is based on the communication infrastructure provided in a typical mobility scenario, such as the Manhattan urban mobility model [26]. Typical external communication of self-driving vehicle includes three main places in Manhattan scenarios: mobile On-Board Units (OBUs), a Trust Authority (TA) equipped on each vehicle and immobile RSUs at the roadside every 250 m as shown in Figure 6[40]:  
* TAs are responsible for authorization communication between RSUs and vehicles. They contain all vital information about traffic statistics and streets. The Certificate Revocation List (CRL) is  
Figure 5: Intrusion Detection System (IDS) Architecture.  
published periodically by the TAs to their RSUs and it has the capability of detecting, receiving and communicating messages to TAs. The TAs and RSU are the building blocks of the system and are considered trusted entities of the system.
* RSUs provide the backbone communication of self-driving vehicles. These vehicles depend heavily on these vital units in VANETs. The wired communication between immobile infrastructures on the road site with TAs is an authentication feature [40].
* Every vehicle is equipped with an Identification On-Board Unit (ID-OBU), which allows it to share local traffic data and control information between vehicles in their radio zone.  
The data link layer provides continuous monitoring for malicious situations to manage potential risk/hazards. Thus, when malicious behaviour is detected the system is put into. Our system relies on RSUs in emergency because it possesses the following qualities [40]:  
* trusted element because of its wired connection to TAs;
* low delay;
* low bit error rates; and
* high bandwidth.  
The basic addressing and access control to the physical layer are core factors to target the response system on the datalink layer. For malicious behaviour, the response system will configure the communication on point-to-point protocol to allow the infected vehicle to communicate with nearby RSUs. In other words, the response system can partially isolate infected vehicles from other vehicles, and restrict their communication to trust points such as RSUs in that radio coverage area.  
The IEEE 802.11p protocol provides wireless access in vehicular environments. The Protocol is an enhancement to the IEEE 802.11 standard but it is known to have an issue in scalability rate [41]. It cannot offer the required time-probabilistic characteristics in dense road scenarios because it was originally designed for low mobility networks. Thus, the IEEE 802.11p protocol does not operate efficiently for high density and mobility scenarios in VANETs [41]. Alternatively, it has a minimal scalability capability when there are many self-driving vehicles in the same vicinity [42; 43]. Thus, we need to employ the RSU end-points to facilitate in emergency or critical situations.