Date Added: Oct 2011
In recent years, the design and implementation of the wireless sensor networks is widely chosen for research as sensor networks enable application that connects the physical world to the virtual world. Wireless platforms are less expensive and are more powerful, with usage in enabling the promise health science to military sensing operations. The wireless sensor networks are prone to more attacks than wired networks. However, the hardware simplicity of these devices makes defense mechanisms designed for traditional networks infeasible. This paper studies the security aspects of wireless sensor networks. A survey with current threats and countermeasures is carried out, in particular, explored the protocol layer attack on sensor networks.