Wireless Sensor Network is an emerging area that shows great future prospects. Today such networks are used in many industrial and consumer applications, such as military, industrial process, monitoring health and in automated and smart homes. So far, the researchers have only focused on making WSNs useful, feasible, and less emphasis was placed on security. The sensors used are susceptible to different types of attacks, denial of service, physical tampering. In hostile scenarios, it is very important to protect WSNs from malicious attacks. This is the reason we need better security against these challenges, threats and issues in WSN. The intent of this paper is to shed light on the security related issues and challenges in wireless sensor networks investigated by researchers in recent years and that shed light on future directions for WSN security.