  In recent years, wireless sensor network becomes popular both in civil and
military jobs. However, security is one of the significant challenges for
sensor network because of their deployment in open and unprotected environment.
As cryptographic mechanism is not enough to protect sensor network from
external attacks, intrusion detection system (IDS) needs to be introduced. In
this paper we propose a policy based IDS for hierarchical architecture that
fits the current demands and restrictions of wireless ad hoc sensor network. In
this proposed IDS architecture we followed clustering mechanism to build four
level hierarchical network which enhance network scalability to large
geographical area and use both anomaly and misuse detection techniques for
intrusion detection that concentrates on power saving of sensor nodes by
distributing the responsibility of intrusion detection among different layers.
We also introduce a policy based intrusion response system for hierarchical
architecture.
