Quemerford, that is helpful--very helpful. But you were being a little bit over-precise. In ordinary speech, "classified" means having some classification which restricts access, and common understanding would be that "Confidential" would be one such classification, and "Secret" another, more restrictive one. The "or" in the question is to be read in an inclusive sense: "secret, or with any other restrictive classification." This is doubtless not the strict technical usage, but strict technical language is for getting precise jobs done, not for explaining why a question shows that people don't know the technical language, and so don't deserve an answer. The technical situation in which "Unclassified" can be a classification is frankly a bit of a boggler, and reminds me of the problem of the set of all sets that do not contain themselves.
Perhaps my tone is objectionably pedagogic?