Security is the primary and integrated requirement for public networks. Internal authenticated attackers are more unfriendly and dangerous to the network. In this paper, a probabilistic Dempster Shafer method is applied to the communication behaviour of network nodes. A prior analytical observation over the communication was done in terms of upper and lower bounds. The upper bound is considered as the belief measure and the lower bound is taken as plausibility factor. The probabilistic belief-to-plausibility measure is obtained for communication delay, failure ratio and energy parameter. As the abnormal activity pair was identified, a verification check was performed before blocking the misbehaving node. The Dempster-Shafer based belief theory was applied to isolate the attacker node and to generate the safe path over reliable nodes. The decision rule was integrated to the work behaviour of the AODV (Ad hoc On-Demand Distance Vector) protocol for the preventive route formation. The simulation results show that the method has improved the communication PDR (Packet Delivery Ratio) ratio and reduced the drop rate and energy consumption as compared to AODV and DSR (Dynamic Source Routing) protocols.