In this paper, we propose an obligation-based model called fellowship to mitigate the flooding and packet drop attacks. We also explain how the fellowship model identifies and penalizes both the malicious and selfish nodes respectively in mobile ad hoc networks (MANET). The main advantages of our model are: it unifies the framework to defend both flooding and packet drop attacks, it identifies and expels the malicious and selfish nodes that fail to contribute their resources, and rejoins the repenting malicious and selfish nodes into the network. In addition, our technique does not rely on any centralized authority or tamper-proof hardware.