One of the most popular areas of research is wireless communication. Mobile Ad Hoc network (MANET) is a network with wireless mobile nodes, infrastructure less and self organizing. With its wireless and distributed nature it is exposed to several security threats. One of the threats in MANET is the wormhole attack. In this attack a pair of attacker forms a virtual link thereby recording and replaying the wireless transmission. This paper presents types of wormhole attack and also includes different technique for detecting wormhole attack in MANET..