In body biosensor networks, which may be classified as a specialized type of ad hoc networks, it is necessary to ensure the authenticity and freshness of the vital medical information. In this work, we propose security solutions to identify attacks on data freshness and preserve message integrity in these networks. We use the measurement of permissible round trip time threshold and computationally feasible authentication solution to address the security threats in the network. We have implemented a prototype framework in GloMoSim to assess and evaluate the robustness of our detection mechanism.