Enhanced Secure Hash based Client Puzzle approach to defend against Cyber Attacks M.Uma Ph.D Research Scholar Department of Computer Science Avinashilingam Institute for Home Science and Higher Education for Women Coimbatore -641043 Dr.G.Padmavathi Professor and Head Department of Computer Science Avinashilingam Institute for Home Science and Higher Education for Women Coimbatore -641043 ABSTRACT Game theory is a widely used technique for network security. As technology grows, the cyber worlds are more vulnerable to unknown cyber attacks. There are many cyber attack detection methods available for known attacks; however, efficient methods are essential to detect the unknown cyber attacks. In this research work, an enhanced hash based game theory approach is introduced to defend against cyber attacks. The proposed method is tested in a simulated environment and the method is evaluated using the performance metrics like Throughput, End to end delay, Packet delivery ratio, routing overhead, energy consumption and latency. KEYWORDS: Game theory, Client puzzle, Hash Chain, Cyber Attacks, Elliptic curve cryptography 1. INTRODUCTION Passive attack is a process of hacking the communicated data without giving any alerts [1]. There will not be any mess up in the network. There are still more challenges in detecting the passive attacks. Traffic monitoring, Eavesdropping, Traffic analysis and Syn flooding are the termed as passive attacks [2] [3]. Though many methods are available some more efficient techniques are still needed to handle unknown cyber attacks. Now a days, as technology grows the vulnerability also higher for hacking the data or information. In the year 2009, in cyber leap year summit it is suggested that game theory plays a (IJCSIS) International Journal of Computer Science and Information Security, Vol. 13, No. 8, August 2015 57 http://sites.google.com/site/ijcsis/ ISSN 1947-5500