Ad hoc networks are those that have mobile nodes. They do not have a static topology and dynamically changing by nature. Mobile Ad hoc Networks (MANET) do not have a centralized administrator too. For this nature MANET is much prone to security attacks such as DoS, Eavesdropping, black hole, gray hole, worms etc. In this paper, we have a glance on all types of attacks on MANET and we provide a scheme which focuses on security of MANETs by echoing and path refreshing by detecting black holes. We also introduce an algorithm for the same based on echoing of neighboring nodes. The proposed algorithm is successfully attempted to detect and remove black holes in MANETs.

Keywords : MANET, Byzantine attack, black holes, worms.