A Mobile Ad hoc NETwork (MANET) is an intelligent automated dynamically distribution of wireless Mobile independent nodes they either connect straightforwardly or utilizing halfway node(s) without any predefined infrastructure. If there is no predefined infrastructure then networks get unprotected to number of attacks and elevated amount security turns into a real concern. The first section discusses brief introduction, features and routing protocols of MANET. The second section discusses the vulnerabilities in MANET. Mobile Ad-hoc NETwork (MANET) is one of the most necessary fields for study, development and research of wireless networks.