Both state and non-state parties face the imposing threats from the weaponization and illegal intrusion of UAS. The development of Counter-UAS, or C-UAS, in particular, Counter-Small UAS to detect, track, and intercept drones has become an urgent mission. The article discusses the challenges in the current C-UAS market and evaluates various approaches incorporated into the C-UAS, including LWIR, MWIR Passive Thermal Imaging and other approaches like radar, visual cameras, SWIR imaging.