Security threats and their defense metrics for wireless sensors

Wireless Sensor Network consists of distributed autonomous sensor nodes to monitor physical and environmental conditions, Such as temperature, sound, vibration, pressure, motion and to collectively pass their data through the network to a main location known as Base station or Sink. Wireless sensor consist of huge number of nodes spread over diverse locations having characteristics like low processing power, low storage capacity and limited battery life. That means sensor networks are battery powered. As a sensor network grows it is more suspected to attacks. Sensor nodes will communicate highly sensitive data among various nodes, so it is most important to construct a secure channel for a wireless sensor network. They are mostly used in applications, such as military monitoring, health care as well as civilian applications. The main aim of this paper is to investigate the security related issues in wireless sensor networks .This paper categories various security threats and their classification that can occur in wireless sensor networks and providing probable Countermeasures (defenses) against the attacks.