A　mobile　ad-hoc　network　(MANET)　is　an　ordinary　and　self-orbiting　communication　network　that　is　capable　of　managing　mobile　nodes.　Many　proposed　protocols　on　MANET　address　its　vulnerability　against　different　threats　and　attacks.　The　malicious　node　exploits　these　vulnerabilities　to　lunch　attacks,　especially　when　nodes　have　mobility　and　network　do　not　have　constant　topology,　like　wormhole　attack.　This　paper　presents　a　lightweight　technique　that　detects　the　wormhole　attacks　in　MANET.　In　the　proposed　technique,　the　source　node　calculates　the　average　sequence　number　of　the　reply　(RREP)　packets.　If　the　sequence　number　of　the　corresponding　node　exceeds　the　calculated　average　value　of　the　sequence　number,　then　all　traffic　is　discarded,　and　the　node　is　marked　as　malicious.　The　proposed　technique　is　less　complex,　power-efficient,　and　enhances　network　lifetime　as　more　data　packets　are　delivered　to　the　destination　node.　This　technique　is　validated　through　comprehensive　simulations　results　in　NS2