In this paper, we design a novel secure routing protocol for mobile ad hoc networks (MANETs), called trusted dynamic source routing (TDSR) which extends the widely used DSR routing protocol and employs the idea of trust network connect (TNC) to protect routing behaviors. In the TDSR, trust among nodes is represented by trust score, which consists of direct trust and indirect trust. Trust relationships and routing decisions are based on experienced, observed, or reported routing and forwarding behavior of other nodes. The detailed implementation of TDSR assumes that the network layer is based on DSR. We present a performance analysis of DSR fortified by TDSR and compare it to regular defenseless DSR. It shows that a network with TDSR and up to 60% of misbehaving nodes behaves almost as well as a benign network. All simulations have been implemented and performed in NS2.