Manet is highly vulnerable to distributed denial of service (DDOS) attacks; these DDOS attacks consume all system resources like battery power, bandwidth energy, CPU resources, CPU cycles etc and also makes resources or nodes unavailable to the legitimate users. Therefore these DDOS attacks always affect the network connectivity due to the dynamic nature of the nodes as well as functioning of the network which results in data delivery and packet dropping. Significant efforts have been made for the security of Adhoc network but it will not work always due to the dynamic behavior of nodes in the network. In this paper we will present a deep sight into DDOS attacks and how they affect the MANET, also how BLACKHOLE attack affect the connectivity which is more dangerous than other attacks and how we can make the network more effective by understanding the nature of nodes.