With the global use of wireless sensor network technology in different fields and for different purposes such as health care monitoring, earth sensing, air pollution monitoring, military operations monitoring or surveillance system monitoring, a problem arises. Problem that could negatively impact previously started activities and observations if not handled in a right way. Authors of this paper discuss various vulnerabilities and security threads in different applications of WSN in the real world, such as intrusion, node capture attack, black hole attack or selective forwarding attack. Potential countermeasures are proposed formatted as protocols or architectures for secure transfer of data between friendly nodes, compromises on security measures with the goal of achieving secure and reliable connection. This paper could be used as a general representation of WSN security issue with which WSN engineers are faced on a daily basis.