Flying Ad-hoc Networks (FANET) is an evolving phenomenon in the types of ad-hoc networks, which connects Multiple UAVs (Unmanned Aerial Vehicles) or drones. It is a rapidly deployable, infrastructure-less, self-configurable, and flexible communication environment for data transmission among the multi-UAVs and the Base Station (BS). As a result of technological advancement, the deployment of Multi-UAV networks or FANET has increased. Particularly in life-threatening applications like disaster management and military operations, this kind of ad-hoc network will be highly beneficial. Due to its characteristics of infrastructure-less and non-hierarchical behavior, FANETs faces several security issues in their flexible data communication. Since these kinds of networks are significantly emerging, there is a vital need to establish a threat model capable of identifying vulnerabilities, quantifying risks, and addressing them. In Existing observations, these FANET environment are highly vulnerable to any kind of security threats which in turn degrades the overall performance of the network. Securing the data packets in FANET communication is a crucial task because the nodes involved in this network are movable. Malicious nodes can compromise the confidentiality, availability, and integrity of the network by intruding and modifying data or discarding network packets. In this article, the classification of attacks and several security issues for the FANETs are highlighted. Then the experimental analysis of Packet-loss based detection and Content-Modification detection in the FANETs are implemented and discussed using Omnet++ simulation tool.