Communication is vital for transfer or sharing of knowledge between the individuals. Before the invention of telephone and other technological communication device the traditional methods of communication used to be radio or direct meeting of the individual. Later on telephone, mobiles and other devices came to play to minimize the burden to reach out the individual at the same time security became an issue as the channel used by the mobiles and other devices can be tampered so security for the communication also became an factor that is to be kept in mind.There are several methods and attacks that an attacker uses on the network that is used for communication to disturb or alter the communication between the sender and the receiver. The network that we are going to discuss is Mobile Ad-hoc Networks (MANET). The attack that is simulated is Gray Hole attack. Gray hole attack is high level transformation of general black hole in networks that are performed on Wireless Sensor Network (WSN).