Due to the lack of data storage and power sensor networks introduce severe
resource constraints. These are the obstacles to the implementation of traditional computer
security techniques in a WSN. Security defenses harder in WSN due to the unreliable
communication channel and unattended operation. As a result these networks require some
unique security policies.Cryptography,steganography and other basics of network security and
their applicability can be used to address the critical security issues in WSN. Many researchers
have begun to address of maximizing the processing capabilities and energy saving of sensor
nodes with securing them against attackers.There are different types of attacks designed to exploit
the unreliable communication channels and unattended operation of WSNs. Physical attacks to
sensors play an important role in the operation of WSNs due to the inherent unattended feature.
We explore various types of attacks and threats against WSN.