When I worked at the Pentagon a few years ago, a lot of the low-level custodial work I saw done by people I saw were – I don’t know the current socially approved term, so I’ll just use the colloquialism – retarded. Obviously the supervisors weren’t but that does lower the probability that they were undercover spies. Whether or not that resulted from a conscious decision or was just the result of routine contracting policies, I can’t say, but it awfully convenient.
On the subject of classified information, in most places that use it, even inside the Pentagon, there are strict policies in place regarding it. Anything classified must be locked in an approved safe when not under the control of a cleared person, i.e. don’t walk away with something sitting on your desk unless somebody else takes responsibility for it. That sounds awfully formal, but it’s really just a normal, common-sense type of thing
Bill: “Hey Joe, I gotta go get a haircut, I’m leaving some classified out.”
Joe: “Okay, I’ll be here.”
I don’t know from personal experience how it’s actually handled In the few locations that are approved for open storage – where it’s okay to leave classified documents sitting on your desk overnight, – but there are several options available.
As others have mentioned, there will be at least some cleared custodial staff. More likely, routine cleanup is done by the folks that work there, and once a week or so they lock everything classified in a safe so the janitors can come in for a thorough cleanup.
Story I heard once in the Pentagon…
Several Pentagon offices shared a small kitchen where they had coffee pots and a fridge. One day a young private is in the kitchen fetching coffee for some people in his office, when a two-star general comes in. Obviously nervous with the general there, the private slips and spills some coffee. The general smiles and says “Don’t worry son, I’m the lowest ranking one in my offfice too,”