Overview of Security Threats in WSN?

Wireless sensor network is a combination of tiny devices called as sensor nodes which have computing, sensing and processing capabilities. As WSN are deployed in hostile environment usually and can be physically accessible by an adversary; he/she can affect the confidentiality and integrity of the data as well as some other security measures. So security is a main concern in wireless sensor network especially in hostile environment. In this paper we focus on security requirements, security schemes, threats, attacks and their countermeasures that provide protection from those attacks.