MANET is a kind of wireless ad hoc networks, in which mobile nodes operate in dynamic, distributed, and cooperative environment. Open nature of MANET makes it vulnerable to various kinds of attacks. Of these, the most severe are the packet drop attacks such as Blackhole attack, Cooperative Blackhole, and Grayhole attacks. The malicious nodes drop the packets as these packets are routed through them in accordance with the malefic strategy of the particular packet drop attack, which adversely affects the network performance. A substantial amount of research papers focus on dealing with packet drop attacks in the last few years, but security is still an impending issue. In this paper, we have presented the systematic review of the literature of last 6 years on all variants of packet drop attacks. We have classified these techniques into four categories, namely, mathematical based, monitoring based, network dependent, and amalgamation based which are further sub divided into 12 categories. These papers are categorized in a well-defined structure to bring out their contribution, to underline the left-out things, and to foreground the emerging issues for future research. Detailed observations are recorded following a panoptic study in order to identify and divulge more eligible and effective mitigation techniques in a particular environment.