Unattended installation of sensor nodes in the environment causes many security threats in the Ad-hoc networks. The security of the DSR protocol is threaded by a particular type of attack called Black Hole attack. Black hole in Ad- hoc networks is a major problem. The proposed work includes detection and countermeasure rules to make the sensor network secure from these attacks. In our research DSR routing protocol is used to detect which node sends the reply after getting the request packet. This work will lead to minimum delay of packets in simulation results.