A MANET is an infrastructure-less and self-organizing network, all the nodes of the network are independent without any centralized system to manage them. Nodes dynamically establish paths to one another to communicate among the nodes, relying on the other nodes to keep network connected. Due its structure and dynamic nature, MANETs becomes more vulnerable to various types of attacks and security becomes a vital issue. In this paper, the focus lies on security issues associated to ad-hoc networks which are primarily required to provide secure communication and possible counter measures to prevent the attacks.