[show abstract][hide abstract] ABSTRACT: A Mobile Ad hoc Network is a group of wireless mobile computers in which nodes cooperate by forwarding packets to each other allowing them to communicate beyond direct wireless transmission range. Mobile Ad hoc Networks (MANET) has become an exciting and important technology in recent years because of the rapid proliferation of wireless devices. Security is an important issue for all kinds of networks including the Wireless Ad Hoc Networks. In this paper, we are presenting some of the reasons that have made MANETs more vulnerable to attacks than the traditional wired network. This paper also covers the security attributes and the various challenges to security design. This paper shreds light on some of the security attacks that exists in MANETs. This Paper also proposes Trust Based Security Architecture for MANET.