Jamming is typically referred as an intentional interference attack which is left due to the open nature of u medium. Due to their nature, wireless sensor network are probably the category of wireless networks most vulnerable to radio channel jamming. This intentional interference with wireless transmission launch pad for mounting Denial of Service (DoS) attack on wireless networks. Adversaries with knowledge of protocol specification and network secrets can launch jamming attacks which are difficult to detect. The adversary targets the messages of high priority and huge information when the user is active for short period of time. This real time packet classification is done at physical layer.