Wireless Sensor Network(WSN) is an emerging technology and explored field of researchers worldwide in the past few years, so does the need for effective security mechanisms. The sensing technology combined with processing power and wireless communication makes it lucrative for being exploited in abundance in future. The inclusion of wireless communication technology also incurs various types of security threats due to unattended installation of sensor nodes as sensor networks may interact with sensitive data and /or operate in hostile unattended environments. These security concerns be addressed from the beginning of the system design. The intent of this paper is to investigate the security related issues in wireless sensor networks. In this paper we have explored general security threats in wireless sensor network with extensive study.