  This paper proposes a combination of an Intrusion Detection System with a
routing protocol to strengthen the defense of a Mobile Ad hoc Network. Our
system is Socially Inspired, since we use the new paradigm of Reputation
inherited from human behavior. The proposed IDS also has a unique
characteristic of being Semi-distributed, since it neither distributes its
Observation results globally nor keeps them entirely locally; however, managing
to communicate this vital information without accretion of the network traffic.
This innovative approach also avoids void assumptions and complex calculations
for calculating and maintaining trust values used to estimate the reliability
of other nodes observations. A robust Path Manager and Monitor system and
Redemption and Fading concepts are other salient features of this design. The
design has shown to outperform normal DSR in terms of Packet Delivery Ratio and
Routing Overhead even when up to half of nodes in the network behave as
malicious.
