Abstract: Wireless Sensor Network (WSN) is a group of smart sensors, each capable of sensing, processing and communicating, but when deployed in numbers, form a network which collectively monitor the state of the physical world. Its applications and potential benefits are tremendous and seem only limited by imagination. As any technology at its infancy stage, there are plenty of challenges and obstacles lying ahead .The intent of this paper is to investigate the security related issues and challenges in wireless sensor networks. We identify the security threats, review proposed mechanisms for wireless sensor networks.

Keywords: WSN, Applications, Security, Attack , Holistic , Challenges.