In this report, we describe a severe Mobile Ad Hoc Network (MANET) routing attack called a wormhole attack and review state-of-the-art ways to thwart wormhole attacks. In a wormhole attack, intruders tunnel the data from one end of the network to the other, leading distant network nodes to believe they are neighbours and making them communicate through the wormhole link. Unlike many other attacks on ad hoc routing, a wormhole attack can not be prevented with cryptographic solutions because intruders neither generate new, nor modify existing, packets, but rather forward existing ones.
