The mobile ad-hoc network (MANET) is the ad-hoc technology for the automatic connectivity of the nodes in the network cluster. The MANETs are considered as the infrastructure less technology, which uses the peer-to-peer connectivity mechanism for the establishment of the inter-links between the network nodes. The MANET data is propagated over the paths established through the routing algorithms. There are several routing algorithms, which are primarily segmented in the two major groups, reactive and proactive. The reactive networks are designed to query the path when its required, whereas the proactive routing protocol constructs the pre-computed route based routing table, which is utilized to propagate the data over the pre-derived links/routes. In this paper, the major routing protocols have been evaluated for their performance under the distributed denial of service (DDoS) attacks. The advance on-demand distance vector (AODV) and temporally ordered routing algorithm (TORA) protocols, which are considered as one of the best protocols. This paper focuses upon the assessment of the best routing protocol under the DDoS attack over the MANETs. The security and vulnerability analysis of the routing protocols plays the vital role in the security enhancement of the aimed routing protocols. The security evaluation has been based upon the targeted protocols based upon the various factors.