  Security is important for many sensor network applications. Wireless Sensor
Networks (WSN) are often deployed in hostile environments as static or mobile,
where an adversary can physically capture some of the nodes. once a node is
captured, adversary collects all the credentials like keys and identity etc.
the attacker can re-program it and replicate the node in order to eavesdrop the
transmitted messages or compromise the functionality of the network. Identity
theft leads to two types attack: clone and sybil. In particularly a harmful
attack against sensor networks where one or more node(s) illegitimately claims
an identity as replicas is known as the node replication attack. The
replication attack can be exceedingly injurious to many important functions of
the sensor network such as routing, resource allocation, misbehavior detection,
etc. This paper analyzes the threat posed by the replication attack and several
novel techniques to detect and defend against the replication attack, and
analyzes their effectiveness in both static and mobile WSN.
