Unmanned Aerial Vehicles (UAVs), popularly known as drones, are widely used for safe aims and some sensitive missions such as monitoring of critical infrastructure, surveillance operations, and cargo delivery. However, technology can be used for terrible objectives, particularly in recent years when it has become the most essential tool in battles such as the Ukraine conflict. This prompted it to resort to the monster of war. Drones are becoming more and more useful, yet there are security concerns. Drones are a serious threat to public safety, personal privacy, and national security because they can be physically attacked, jammed, or even hacked. This paper provides an empirical review of the security threats that UAVs face, as well as the risks associated with employing drones for cyber-attacks, malevolent objectives, terrorism, military, and war. The study classified the UAV security threats as internal threats and external threats, discussed risk mitigation, and provided effective techniques for establishing a preventive plan against security vulnerabilities to drones. Also suggested a defensive security solution based on trust UAV architecture, which incorporates trust and security into the early stages of UAV design. This enables a preventive UAV architecture against internal security threats and risks.