The use of wireless links furnishes a VANET unsafe to malicious attacks for example Denial of Service, black hole attack, Sybil attack, selective forwarding and altering routing information. In Vehicular Networks are contemplated as the unique class of wireless networks, also called as VANET. It is a major part of Intelligent Transport System (ITS). VANET technology is recognized for enhancing road safety and transport efficiency. But, there are huge security issues in VANET, therefore, there must be a reliable way for communication which is quite tedious and important concern. In this review article, we studied Black Hole attacks under CBR/UDP traffic pattern using various protocols from various research papers of high quality. There are possibilities of various attacks like an active and passive attack on the network to access data. As we know there are many issues in VANET and especially security issues. Our research work will be carried out using NS-2 simulator. Besides this, a detailed study of the attack examined because there are abundant numbers of attack available. These attacks are divided into an active and passive attack and further, these two are classified. In this review paper, we convoluted the diverse class of attacks and their depth in an ad-hoc network.