A survey of survivability in mobile ad hoc networks <s> V. SURVIVABLE INITIATIVES FOR MANETS <s> Intrusion detection has, over the last few years, assumed paramount importance within the broad realm of network security, more so in the case of wireless ad hoc networks. These are networks that do not have an underlying infrastructure; the network topology is constantly changing. The inherently vulnerable characteristics of wireless ad hoc networks make them susceptible to attacks, and it may be too late before any counter action can take effect. Second, with so much advancement in hacking, if attackers try hard enough they will eventually succeed in infiltrating the system. This makes it important to constantly (or at least periodically) monitor what is taking place on a system and look for suspicious behavior. Intrusion detection systems (IDSs) do just that: monitor audit data, look for intrusions to the system, and initiate a proper response (e.g., email the systems administrator, start an automatic retaliation). As such, there is a need to complement traditional security mechanisms with efficient intrusion detection and response. In this article we present a survey on the work that has been done in the area of intrusion detection in mobile ad hoc networks. <s> BIB001 </s> A survey of survivability in mobile ad hoc networks <s> V. SURVIVABLE INITIATIVES FOR MANETS <s> Security in mobile ad hoc networks is difficult to achieve, notably because of the vulnerability of wireless links, the limited physical protection of nodes, the dynamically changing topology, the absence of a certification authority, and the lack of a centralized monitoring or management point. Earlier studies on mobile ad hoc networks (MANETs) aimed at proposing protocols for some fundamental problems, such as routing, and tried to cope with the challenges imposed by the new environment. These protocols, however, fully trust all nodes and do not consider the security aspect. They are consequently vulnerable to attacks and misbehavior. More recent studies focused on security problems in MANETs, and proposed mechanisms to secure protocols and applications. This article surveys these studies. It presents and discusses several security problems along with the currently proposed solutions (as of July 2005) at different network layers of MANETs. Security issues involved in this article include routing and data forwarding, medium access, key management and intrusion detection systems (IDSs). This survey also includes an overview of security in a particular type of MANET, namely, wireless sensor networks (WSNs). <s> BIB002
This section describes several initiatives on building survivable mobile ad hoc networks. Despite that many of them do not present a complete survivable proposal, they have goals, characteristics and mechanisms more correlated to properties and requirements of survivability than just preventive or reactive schemes. Since some papers survey conventional security defense lines BIB002 ,  ,  , BIB001 , this work focuses on security propositions that aggregate more than one defense line and apply some technique of tolerance as redundancy or recovery. Initiatives found in the literature are categorized on three main groups: route discovery, data forwarding, and key management and access control. The route discovery group consists of approaches trying to make route discovery phase of routing protocols more resistant and tolerant to different kinds of attacks and intrusion. The data forwarding group is composed of initiatives specialized on data forwarding using preventive or reactive security schemes and some tolerance techniques, as redundancy. The last one includes cryptographic key management and access control approaches built to be more tolerant to attacks.