Imagine the scenario: you’re a security officer working at Los Alamos. You know that spheres are weapon parts. You walk into a technical area, and you see spheres all around! Is that an ashtray, or it is a model of a plutonium pit? Anxiety mounts — does the ashtray go into a safe at the end of the day, or does it stay out on the desk? (Has someone been tapping their cigarettes out into the pit model?)
All of this anxiety can be gone — gone! — by simply banning all non-nuclear spheres! That way you can effectively treat all spheres as sensitive shapes.
I find this to be an interesting problem — simplifying the task so that someone without the technical skills can make a determination about security. It’s frustrating from the vantage point of the scientist, especially because secrecy tends to run counter to our desire to share our work (an important step in advancing an idea) and also because of the observation about secrecy being contagious, like a disease.
I encountered this when I was in the navy. We had some relatively low-level classified material, from a technical standpoint, and all of it was stamped in red ink and stored in red folders. Security — comprised mostly of students-in-waiting, led by a few permanent staff, only had to have a “see red” mentality, rather than any training on whether a sheet of paper was a set of classified specs or a shopping list. I doubt at Los Alamos that the low-level guards worried about whether spheres were research parts — they had just been told that all spheres were a violation.
Look at the reverse, though. We try and classify things ourselves, and that can have a bad end when it comes to security. Take the incidents a few years ago in Boston involving flashy and/or colored lights. The “bomb” finders caused panic, simply because they had a mental image that objects with flashy lights are what bombs look like.