The NY Times discusses the unknown drones flying above my house and others here in New Jersey. One would have assumed that our wizards in DoD would have prepared for something like this. But alas they have spend the last decade on social engineering. Imagine in WW II if the Rad Lab at MIT was focused on hiring the right mix rather than radar systems. Perhaps my father would not have returned from the Pacific.
Now lets discuss what can/should be done. Drones have detectable profiles, optical and thermal. Ground based systems can be difficult but multi-beam sensors can be effective. These things also have an RF profile. They do not just fly around unguided. So identify the profile, monitor it, detect sources and sinks. I worked in this area 60 years ago! What has happened to DoD? Recall 9/11 when one could not get aircraft to defend the homeland. Two AF National Guard planes unarmed!
At some point DoD should be held to account. Their primary goal is defending the United States. In my opinion they have been grossly neglectful.