Give me a break. The information printed on them, for example the 29 approach at EWR denotes a petroleum tank facility just outside the marker. My point was maybe a way of making them accessible to licensed pilots and trainees, something that might keep it away from those who would use it against us..
Pursuant to international treaties, navigation data such as approach procedures are generally available for all. Just FYI, approach procedures are published as textual procedures first and the graphical part produced later. They're available from numerous vendors in all sorts of forms. Same with a variety of aeronautical navigation charts.
After 9/11/01 they removed the directional sign from Rte 3 in Nashua, NH that showed the exit for ZBW, the Boston ARTCC. Good example of security theater that has no practical effect.
Like trying to keep teenage boys from searching the net for porn. Not practical.
No longer being a teenage boy, here's what 30 seconds of searching for nav/porn found for Moscow.