Mobile ad hoc network (MANET) is a group of mobile (or temporarily stationary) nodes which provides the ability to stream voice, data, and video between arbitrary pairs of devices utilizing the others as relays to avoid the need for infrastructure. There are many techniques which are employed in order to provide robust MANET capability like self-forming, link adaptation, transparent IP Networking, and multicast support. Its rapidly changing network topology, which is unpredictable over time, makes MANET vulnerable to wide range of attacks. It is very tedious to detect some attacks when it becomes a part of network. Ad hoc ondemand distance vector (AODV) is a popular reactive routing protocol but exposed to well-known packet dropping attack, where a malicious node intentionally drops packets without forwarding them to destination. In this paper, we discuss the security mechanisms, namely data routing information (DRI), cross-checking, and retard-mode operations, to defend against packet dropping attack in MANET with results simulated in ns-2 to show the improvement in packet delivery ratio.