Since drones first came on the market, we have seen a number of stories about the very real potential for in-flight contact with commercial aircraft, and several temporary airport shutdowns because of reported close-calls. FAA has just posted two new rulemaking notices regarding drones, with comments due April 15, 2019. But from a security perspective, there is an understanding that the good guys will probably follow the rules and airspace operational constraints, all of which are ignored by the bad guys (and just-plain stupid ones) who don’t give a damn about your stinkin’ rules.
I am of the opinion that there is very little airport security can do about them; it’s an FAA airspace issue. Most airport jurisdictions end at the fence line, so if there has been no intervention by then, it’s already far too late. With only a few-pixel reflective profile, standard radar can’t see them coming, and not at all while they are hovering.