www.ijecs.in International Journal Of Engineering And Computer Science ISSN:2319-7242 Volume 3 Issue 12 December 2014, Page No. 9547-9551 Barleen Shinh 1 IJECS Volume 3 Issue 12 December, 2014 Page No.9547-9551 Page 9547 A Review Paper on Collaborative Black Hole Attack in MANET Barleen Shinh 1 , Manwinder Singh 2 Rayat Institute of Engineering and Information Technology Rail Majra Distt. Nawanshar, Punjab 143001 Abstract: Ad-hoc networks have become a new standard of wireless communication in infrastructure less environment. MANET is a Mobile Ad-hoc Network in which the nodes get connected with each other without an access point. Messages are exchanged and relayed between nodes. Routing algorithms are utilized for forwarding packets between indirect nodes i.e not in direct range with aid of intermediate nodes. They are spontaneous in nature and absence of centralized system makes them susceptible to various attacks. Black hole attack is one such attack in which a malicious node advertises itself as the best route to the destination node and hinders the normal services provided by the network. Keywords: Mobile Ad Hoc network, Single Black hole attack, Collaborative Black Hole Attack 1. Introduction A MANET consists of wireless hosts that can be arbitrarily deployed as a multi-hop packet radio network in absence of any infrastructure or centralized system. Some characteristics of MANETs are unreliable wireless media links used for communication between nodes, dynamic network topologies, restraint battery, lifetime of the network, bandwidth and computation power of nodes [1]. MANETs are prone to various types of active and passive attacks. Active attacks are categorized into Interception, interruption, fabrication and modification attacks. A passive attacker does not interrupt with the operation of a routing protocol but puts efforts to gather the vital information from packets. MANET has proactive, reactive and hybrid routing protocols [2]. In proactive protocols the routes to all parts of the network or the destinations is determined at the starting time and a route update table is maintained periodically. Some popular protocols are Destination Sequence Distance Vector (DSDV) and Wireless Routing Protocol (WRP). In reactive protocols the route discovery process is carried out for establishing the routes as and when required. Mostly used protocols are Ad-hoc On Demand Distance Vector (AODV) and Dynamic Source Routing (DSR) [3]. Hybrid protocols Employ a hierarchical strategy these protocols adhere to combination of properties of both proactive and reactive protocol. The most widely used protocols are Ad hoc on-demand distance vector (AODV) routing protocol and Dynamic