Abstract: Mobile ad-hoc network (MANET) is one of the most important fields for development of wireless network. A mobile ad hoc network is an autonomous collection of mobile devices like laptops, mobiles, sensors, etc. MANET is an emerging technology and have great strength to be applied in critical situations in military battlefields and commercial applications such as building traffic system, MANET is infrastructure less, with no any centralized controller exist. So one of the major challenges wireless mobile ad-hoc networks face today is security, because no central controller exists. There are many security attacks in MANET and DDOS (Distributed denial of service) is one important attack in MANET.