Abstract: Wireless Sensor Networks (WSN networks) are becoming an important topic in the eyes of researchers because of its vast variety of applications in various fields. WSNs are application specific networks which have a large number of small, randomly deployed self-configurable sensor nodes, capable of sensing an event, computing and communicating the event details with the neighboring sensor nodes. In many technologies, like Internet of Things (IoTs), WSNs act as a digital skin by which the information about the outside world is obtained. WSNs are used in many applications, in particular, Personal applications like home automation, Business applications like sales tracking, Industrial applications, and military applications etc. So the task of WSN is not only sensing but also the computation of data which is their responsibility and hence the quality of data is very crucial. Since there are no particular criteria for the deployment of sensor nodes, the hostile environments in which they are deployed and their energy constraints, they are very much vulnerable to anomalies and attacks. Any deviation from the normal sensing profile can be considered as an abnormality in the network. This paper gives an overview of such cases in a WSN.

Keywords: Wireless Sensor Networks, Anomalies, Selective Forwarding Attack.