As mobile ad hoc networks (MANETs) are increasingly deployed in critical environments, security becomes a paramount issue. The dynamic and decentralized nature of MANETs makes their protocols very vulnerable to attacks, for example, by malicious insiders, who can cause packets to be misrouted or cause other nodes to have improper configuration. This paper addresses security issues of auto-configuration protocols in ad hoc networks. Auto-configuration protocols enable nodes to obtain configuration information (e.g., an IP address) so that they can communicate with other nodes in the network. We describe a formal approach to modeling and reasoning about auto-configuration protocols to support the detection of malicious insider nodes. With respect to this family of protocols, our approach defines a global security requirement for a network that characterizes the "good" behavior of individual nodes to assure the global property. This behavior becomes local detection rules that define a distributed specification-based intrusion detection system aimed at detecting malicious insider nodes. We formally prove that the local detection rules (identifying activity that is monitored) together with “assumptions” that identify system properties which are not monitored imply the global security requirement. This approach, novel to the field of intrusion detection, can, in principle, yield an intrusion detection system that detects any attack, even unknown attacks, that can imperil the global security requirement.
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