The U.S. Air Force has forcefully reminded military and civilian personnel working at Edwards Air Force Base that it is forbidden to point unauthorized sensors at "low observable" or "sight sensitive" aircraft being tested at the base. Edwards is where the air force tests its stealth and other "black" (top secret) projects. "Low observable" means stealth, while "sight sensitive" means secret aircraft that even a picture of could reveal details of what it could do.
The "sensors" refer to cameras, audio recorders, radars or whatever. What has the brass on edge is the proliferation of very capable digital camera (still and motion) and audio recorders in the hands of anyone. Consumer electronics are capable to taking much more detailed pictures, or sound samples. The air force personnel at Edwards are a bright bunch, and some build their own sensors (like radars) just for the hell of it. What scares the brass most, is some young airman posting high resolution digital pictures, or videos, of some new aircraft, on the Internet. Thus the warning. Do it, and get caught, and you are toast.