In this paper, two routing protocols (AODV and DSR) are simulated under regular operation, single and cooperative black hole attack. This work has been performed by simulator to show consequence of black hole attacks in MANET by using various graphs which are used to collect data in term of several metrics. One common method to perform most of researches in the MANET security field is to simulate and analyze the routing protocols in various scenarios. This work has been based on the implementation and experiments in the OPNET modeler version 14.5. Finally the results have been computed and compared to stumble on which protocol is least affected by these attacks.