Wireless Sensor Network (WSN) is incorporated in various areas like military, traffic surveillance, healthcare, and monitoring the environmental conditions. Limited battery and low memory are some inherent features which builds impracticable sensor network and it will reduce the communication inefficient. Data attacks related to the sensor nodes which affects the WSNs are wormhole, packet drop and selective forwarding attack. In a packet drop (black hole) attack, one node acts as malicious and also it drops the packets which are forwarded through it. A uniquecharacteristicof this attack is in which the mischievous node drops packets selectively. Network layer is the middle layer that coordinates the lower and upper layers whichplays a vital role for providing the security of WSNs to prevent exploitation of their all kinds of security services. It is importantto analyze and mitigate the security loopholes ofWSNs on the network layer, particularly selective forwarding attacks.