Wireless Sensor Network (WSN) consists of low cost sensor nodes which cannot afford to implement sophisticated security system in it. That is why intrusion detection architecture for WSN is considerably different and difficult to implement. Most of the current implementations are based on exchanging anomaly signals among the leaf level sensors resulting in too much power consumption. We propose a novel architecture for Intrusion Detection System (IDS) in WSN based on Hierarchical Overlay Design (HOD) that will distribute the overall responsibility of intrusion detection into entities and thus conserve memory and power of the nodes. The architecture uses layered design with GSM cell like structure based on special monitor nodes. The HOD structure enables the sensors to communicate using far less messages and thus conserve precious power and also saves memory by not implementing IDS module on each sensor. The proposal also uses rippling of alarm through layers and thus ensures proper delivery to the uppermost layer with redundancy.