Counter-drone systems cannot distinguish a $500 attack drone from a $2 civilian hobby drone — so they shoot down both or neither

An airbase detects an incoming small drone on radar. Is it a $500 FPV drone carrying explosives or a $200 DJI Mini flown by a hobbyist who wandered into restricted airspace? The radar signature is identical. The drone is too small to visually identify at range. The base commander has 30 seconds to decide: shoot it down (risk killing a civilian, waste a $100K missile on a toy) or let it pass (risk a successful attack). In practice, most bases let it pass because the false positive rate is 90%+ — for every real threat, there are 9 hobby drones. So what? The proliferation of consumer drones has created a needle-in-a-haystack problem for air defense. Any $500 drone is a potential weapon. There are 800,000+ registered drones in the US alone and millions unregistered. Current counter-drone systems (Coyote interceptor: $100K, microwave: $1M+, laser: $500K+) are too expensive to use against every detected drone. Kinetic intercept over populated areas risks collateral damage. RF jamming affects friendly communications. There is no scalable, cheap, accurate way to detect, classify, and neutralize hostile small drones in a mixed airspace with civilian traffic. Why does this persist? Small drones have the same radar cross-section as birds. Acoustic detection works within 500m but not beyond. Visual AI classification requires line-of-sight. RF detection only works if the drone is actively communicating (autonomous drones are RF-silent). The physics of detection fundamentally favor the attacker: small, cheap, numerous objects are hard to find and expensive to neutralize.