A MANET is a cooperative network in which each node has dual responsibilities of forwarding and routing thus node strength is a major factor because a lesser number of nodes reduces network performance. The existing reputation based methods have limitation due to their stricter punishment strategy because they isolate nodes from network participation having lesser reputation value and thus reduce the total strength of nodes in a network. In this paper we have proposed a mathematical model for the classification of nodes in MANETs using adaptive decision boundary. This model classifies nodes in two classes: selfish and regular node as well as it assigns the grade to individual nodes. The grade is computed by counting how many passes are required to classify a node and it is used to define the punishment strategy as well as enhances the reputation definition of traditional reputation based mechanisms. Our work provides the extent of noncooperation that a network can allow depending on the current strength of nodes for the given scenario and thus includes selfish nodes in network participation with warning messages. We have taken a leader node for reputation calculation and classification which saves energy of other nodes as energy is a major challenge of MANET. The leader node finally sends the warning message to low grade nodes and broadcasts the classification list in the MANET that is considered in the routing activity.
 Y. Hu, A. Perrig and D. Johnson, “Ariadne: A Secure On-Demand Routing Protocol for Ad Hoc Networks,” Proceedings of the 8th Annual International Conference on Mobile Computing and Networking, September 2002, pp. 12-23. doi:10.1145/570645.570648
 K. Sanzgiri, B. Dahill, B. Levine, C. Shields and E. Belding-Royer, “A Secure Routing Protocol for Ad Hoc Networks,” The 10th IEEE International Conference on Network Protocols (ICNP), 12-15 November 2002, pp. 78-87.
 Y. Hu, D. Johnson and A. Perrig, “SEAD: Secure Efficient Distance Vector Routing in Mobile Wireless Ad Hoc Networks,” The 4th IEEE Workshop on Mobile Computing Systems and Applications, June 2002, pp. 3-13.
 C. E. Perkins and E. Royer, “Ad-Hoc On-Demand Distance Vector Routing,” Proceedings of 2nd IEEE Workshop on Mobile Computing Systems and Applications, 1999, pp. 90-100. doi:10.1109/MCSA.1999.749281
 S. Marti, T. J. Giuli, K. Lai and M. Baker, “Mitigating Routing Misbehavior in Mobile Ad Hoc Networks,” Proceedings of the 6th Annual International Conference on Mobile Computing and Networking (ACM MobiCom 2000), New York, 2000, pp. 255-265.
 S. Buchegger and J. Y. Le-Boudec, “Nodes Bearing Grudges: Towards Routing Security, Fairness, and Robustness in Mobile Ad Hoc Networks,” Proceedings of the 10th Euromicro Workshop on Parallel, Distributed and Network-Based Processing, Canary Islands, 2002, pp. 403-410.
 P. Michiardi and R. Molva, “CORE: A Collaborative Reputation Mechanism to Enforce Cooperation in Mobile Ad-Hoc Networks,” In: J.-B., Borka and K. Tomaz, Eds., Advanced Communications and Multimedia Security, Kluwer Academic Publishers, 2002.
 F. Wang. F. R. Wang, B. X. Huang and L. T. Yang, “COSR: A Reputation-Based Secure Route Protocol in MANET,” EURASIP Journal on Wireless Communications and Networking—Special Issue on Multimedia Communications over Next Generation Wireless Networks Archive, Vol. 2010, 2010, pp. 1-11.
 S. R. Zakhary and M. Radenkovic, “Reputation Based Security Protocol for MANETs in Highly Mobile Disconnection-Prone Environments,” International Conference on Wireless On-demand Network Systems and Services (WONS), 2010, pp. 161-167.
 M. A. K. Akhtar and G. Sahoo, “A Novel Methodology for Securing Adhoc Network by Friendly Group Model,” The 4th International Conference on Networks & Communications (NetCoM), Chennai, September 2012.
 A. Mitrokotsa and C. Dimitrakakis, “Intrusion Detection in MANET Using Classification Algorithms: The Effects of Cost and Model Selection,” Ad Hoc Networks, Vol. 11, No. 1, 2013, pp. 226-237. doi:10.1016/j.adhoc.2012.05.006
 E. Hernández-Orallo, M. D. Serrat, J.-C. Cano, C. M. T. Calafate, and P. Manzoni, “Improving Selfish Node Detection in Manets Using a Collaborative Watchdog,” IEEE Communications Letters, Vol. 16, No. 5, 2012, pp. 642-645. doi:10.1109/LCOMM.2012.030912.112482
 E. Hernández-Orallo, M. D. S. Olmos, J.-C. Cano, C. T. Calafate and P. Manzoni, “Evaluation of Collaborative Selfish Node Detection in MANETS and DTNs,” MSWiM’12 Proceedings of the 15th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems, 2012, pp. 159-166.
 C.-T. Li, C.-C. Yang and M.-S. Hwang, “A Secure Routing Protocol with Node Selfishness Resistance in MANETs,” International Journal of Mobile Communications, Vol. 10, No. 1, 2012, pp. 103-118. doi:10.1504/IJMC.2012.044525
 H. Yu, Z. Q. Shen, C. Y. Miao, C. Leung and D. Niyato. “A Survey of Trust and Reputation Management Systems in Wireless Communications,” Proceedings of the IEEE, Vol. 98, No. 10, 2010, pp. 1755-1772. doi:10.1109/JPROC.2010.2059690