Ad hoc networks have a wide array of military and commercial applications. They are ideal in situations where installing an infrastructure network is not possible or when the purpose of the network is too transient or even for the reason that the previous infrastructure network was destroyed.Security in mobile ad hoc networks is a hard to achieve due to dynamically changing and fully decentralized topology as well as the vulnerabilities and limitations of wireless data transmissions. Existing solutions that are applied in wired networks can be used to obtain a certain level of security. Nonetheless, these solutions are not always be suitable to wireless networks. Therefore ad hoc networks have their own vulnerabilities that cannot be always tackled by these wired network security solutions. One of the very distinct characteristics of MNs is that all participating nodes have to be involved in the routing process. Traditional routing protocols designed for infrastructure networks cannot be applied in ad hoc networks, thus ad hoc routing protocols were designed to satisfy the needs of infrastructureless networks. Due to the different characteristics of wired and wireless media the task of providing seamless environments for wired and wireless networks is very complicated. One of the major factors is that the wireless medium is inherently less secure than their wired counterpart. Most traditional applications do not provide user level security schemes based on the fact that physical network wiring provides some level of security. The routing protocol sets the upper limit to security in any packet network. If routing can be misdirected, the entire network can be paralyzed. This problem is enlarged in ad hoc networks since routing usually needs to rely on the trustworthiness of all nodes that are participating in the routing process. An additional difficulty is that it is hard to distinguish compromised nodes from nodes that are suffering from broken links.