Ad hoc networks in general have to deal with a highly decentralized as well as a continuously changing topology due to the mobility of the nodes. MANET is not a new paradigm in wireless community. The technology is quite old but still practical implementation is difficult due to security and other problems. Since the ad hoc environment is very vulnerable to a multitude of different attacks, new methods of securing these network environments have to be developed. Mobile ad hoc networks or MANETs are supposed to play an important role in future military communication, natural disaster, isolated areas and many more. But while offering many advantages, the MANET technologies today are facing new security threats. Only one malicious node can be sufficient to distort operation in a MANET not using any security mechanism. Number of different algorithms and solution are available, but, realization of robust security architecture is impossible without proper understanding of possible threats and their consequences.