None of which are universally effective. Some rely upon RF detection, others the presence of IR illumination, and yet others the reflection of the CMOS chip. B

None of which are universally effective. Some rely upon RF detection, others the presence of IR illumination, and yet others the reflection of the CMOS chip. But, a hardwired camera with no active illumination, behind an opaque sheet of IR transparent plastic (basically the kind of plastic on many modern electronics) would be incredibly hard to detect (without tearing everything apart).