In wireless sensor networks, wirelessly nodes communicate with each other. WSN is a very large array of diverse sensor nodes that are interconnected by a communication network . The battery lifetime of nodes in wireless sensor networks have limited, the focus must always be given to conserve their energy so that they can work for longer duration of time. While some of the attacks such as black hole attack or worm hole attack focus on the dropping the data packets which are being transmitted in the network, other attacks such as hello flood attack focus on consuming up the resources of the network like battery power of the nodes etc. These kind of attacks prove to be very harmful to the network. In wireless sensor network, By the use of LEACH protocol nodes are usually clustered in the groups. This technique is applied in most of the cases to conserve the energy of the nodes. Hello flood attack is one common misbehaving activity which targets the cluster head which are formed in the clusters of the wireless sensor network. This study presents the detection and prevention of hello flood attacks by use cenetralized technique in wireless sensor networks