Abstract: Mobile Ad-hoc Network is a volatile infrastructure network. It is dynamic in nature i.e. it consists of movable nodes. Due to its changing topology it tends to get attacked by unauthorized access. Among various attacks routing attack is the one which causes severe damage to the network infrastructure. There exist a number of techniques and methodologies to overcome this problem but almost all these techniques concentrates on isolating the node at the instant it is being attacked which further ruins the network. In this paper, a filtering technique is proposed to reduce the permanent isolation of nodes.