In　order　to　detect　various　kinds　of　malicious　attacks　in　wireless　sensor　networks,　we　proposed　a　group　based　intrusion　detection　scheme　which　meets　the　efficient,　lightweight　and　flexible　property　in　this　paper.　The　sensor　networks　are　partitioned　into　many　groups　in　which　the　sensors　in　each　group　are　physically　close　to　each　other　and　equipped　with　the　same　sensing　capability.　Our　intrusion　detection　algorithm　takes　into　consideration　of　multiple　attributes　of　the　sensor　nodes　simultaneously　to　detect　malicious　attackers　precisely.　We　show　through　experiments　with　real　data　that　our　algorithm　can　decrease　the　false　alarm　rate　and　increase　the　detection　accuracy　rate　compared　with　existing　intrusion　detection　schemes　while　lowering　the　power　consumption.