## 5 SDN-based VANETs Security Challenges
### Denial of Service Attacks (DoS)  
This is the most conspicuous attack. The adversaries keep a particular hub from getting to administrations. The DoS attacks [56] are the most renowned and hazardous in the vehicular system, where the assailants send enormous solicitations to the framework so as to close down the system and stop correspondence among vehicles and among vehicles and RSUs. The objective of DoS is to quit sending or accepting data to vehicles about the system, for example, street status. As SDN-based VANETs manage content names rather than Internet Protocol (IP) addresses, DoS attacks depend on the utilization of names [11] and may target customers, makers, or middle-of-the-road hubs. From the SDN-based VANET's perspective, a fundamental DoS attack could be Interest flooding, where an assailant sends a tempest of Interest requesting an alternate substance that may not be accessible in the reserve store. Figure 12 describes a straightforward DoS attack; vehicles, RSUs, and other system foundation components are associated with this situation. However, because of the Interest collection, middle-of-the-road hubs may have increasing opportunity to be focused or contrasted with the substance supplier, particularly while mentioning a phony substance (i.e., content with a substantial name prefix and invalid addition). The aftereffect is Interest dropping at the supplier level and pending interest table passages after lifetime termination at the middle-of-the-road hubs level. In any case, mentioning a unique substance that ought to be created by the first substance supplier after getting the Interest (e.g., requesting a new patient report) may cause DoS at the supplier level because of the way that the dynamic substance is not well known and may not be collected by middle hubs. A pernicious vehicle sends a tempest of various Interests requesting diverse substance names, as an RSU does not have the substance, and it advances the solicitation and makes another request. In light of the immense number of malignant interests, an authentic vehicle cannot send more demands and may not profit from the store abilities of the RSU or on occasion send its solicitations to different hubs. The attack is progressively serious with regards to delicate and critical correspondences that may influence an individual's life. Different countermeasure arrangements have been proposed to survive and alleviate DoS attacks, by utilizing either rate constraining systems (e.g., per face or per name-prefix) [78] or factual displaying approaches. The previous comprises of checking the face/name-prefix break rates as well as the pending interest table size, when distinguishing DoS attacks, and as far as possible the intrigue appearance rate (IAR) on the suspicious face, while the last depends on factual data about the request and interfaces to recognize the irregular traffic design. However, these arrangements need to make a broad adjustment to the ordinary request structure or inordinate stockpiling insights [78]. Distributed Denial of Service (DDoS)  
SDN-based VANET structures [56] are defenseless against DDoS attacks. Since SDN-based VANET structures are divided into three primary practical layers--foundation plane (vehicles, RSUs), control plane (RSU controller), and the application plane--probable DDoS attacks could be propelled on any one of these planes. To quickly assist the DDoS, one may utilize the arrangement of [PERSON] et al. [79], who developed an AI method for DDoS recognition. Specifically, the stream measurements are gathered from switches or from the vehicle sensors and afterward prepared. Although utilizing such an answer at vehicles could be dangerous because of the asset requirement nature of the sensors when contrasted and the nonexclusive SDN switch. Another arrangement, flood-protect, comprises counteracting DDoS attacks by utilizing information relocation and the information plane reserve.