A Semi-distributed Reputation Based Intrusion Detection System for Mobile Adhoc Networks

A Mobile Adhoc Network (manet) is a coop- erative engagement of a collection of mobile nodes without any centralized access point. The underlying concept of coordination among nodes in a cooperative manet has in- duced in them a vulnerability to attacks due to issues like dynamically changing network topology, cooperative algo- rithms and lack of centralized monitoring point. We pro- pose a semi-distributed approach towards a reputation-based Intrusion Detection System (ids) that combines with the Dy- namic Source Routing (dsr) protocol for strengthening the defense of a manet. Our system inherits the features of rep- utation from human behavior, hence making the ids socially inspired. It has a semi-distributed architecture as the crit- ical observations of the system are neither spread globally nor restricted locally. The system assigns maximum prior- ity to self observation by nodes for updating any reputation parameters, thus avoiding the need of a trust relationship be- tween nodes. Our system is also unique in the sense that it features the concepts of Redemption and Fading with a ro- bust Path Manager and Monitor system. Simulation studies show that dsr fortied with our system outperforms normal dsr in terms of the packet delivery ratio and routing over- head even when up to half of nodes in the network behave as malicious. Various parameters introduced such as timing window size, reputation update values, congestion parameter and other thresholds have been optimized over several simu- lation runs. By combining the semi-distributed architecture and other design essentials like path manager, monitor mod- ule, redemption and fading concepts, our system proves to be robust enough to counter most common attacks in manets.