A Selective packet drop attack is notorious security problem in wireless Mobile Ad-Hoc network (MANET). A mobile Ad-Hoc network is wireless networks without any pre-existing infrastructure and centralizes control. They have self-organizing capabilities with mobile nodes. Ad-Hoc network contains multi-hop routes capabilities within short transmission range. Because of openness nature MANET is malicious by attacker. Several approaches have been proposed for finding malicious activity in MANETs. Due to nonexistence of MANETs infrastructure and well defied perimeter MANETs are susceptible to variety of attacker types. To develop a mechanism which provide strong security and understand the malicious node activity in the MANETs. A new mechanism presented is called KEAM (Key Exchange and Monitoring), which isolate malicious node on selective path in AODV routing protocol and secure the channel. This new methodology is named as “Isolate and prevent Selective Packet Drop Attack in MANETs. It is based on Diffie-Hellman Key exchange and monitor mode technique. Experimental result will be drone with use of NS-2 simulator and simulate result for Throughput, Packet loss, End-to- End Delay and compare the result with existing technique