Combining filtering techniquesin wireless sensor network

Wireless sensor networks (WSNs) are widely used in many applications including military surveillance, habitat monitoring, and health care.WSNs are usually composed of a large amount of sensor nodes with limited resources, and are usuallydeployed in unattended environments. In such environments, the security of sensor nodes is very important. Once a node is compromised, the adversary will disclose all the secret information stored in that node.The adversary can then use the compromised nodes to launch false data injection attacks,i.e. to inject bogus reports intosensor networks. Defending false data injection attacks is an important research issue in WSNs, because this type of attacksnot only causes false alarms that waste real-world response efforts (e.g. sending response teams to the event location), butalso may drain out the constrained resources of the forwarding sensors