Clinton supporters, erroneously, make much out of the idea that of the many, many emails that passed through her private server, none were “marked” classified. They claim that, when in fact thousands of those same emails are indeed now marked classified, that is just after-the-fact Washington squabbling.
So this new information – that America’s intelligence agencies now say the contents of some of those unmarked emails match the contents of their own classified documents – is a big deal. It also suggests just how Clinton’s unclassified server came to be loaded up with classified material.
Several agencies have told Congress that Hillary Clinton’s home server contained some emails that should have been treated as TOP SECRET because their wording matched sections of some of the government’s most highly classified documents. These reports are the first formal declarations by intel agencies detailing how they believe Clinton violated government rules when highly classified information in at least 22 email messages passed through her unsecured home server.
So how this all work?
There is no physical connection between the U.S. government’s unclassified and classified systems; you absolutely cannot email a document from the dark side to the light. Properly configured, classified systems should not allow for removable media, to lessen the chance for information transfer (one of the reasons Chelsea Manning was able to smuggle out so much classified was because his computer was not properly set up, and included a DVD burner. We still don’t know how Ed Snowden got his documents out.)
Given these restrictions, the way anyone can move information from one system to the other is what’s called “sneakernet,” after the athletic shoes. You print out a marked, classified document, and then retype the parts you like into the unclassified system. You of course do not add the marking – TOP SECRET – because that would be like robbing a bank and then sticking a sign on your chest saying “Attention Cops, I’m the Guy Who Just Robbed a Bank.” Including the classification markings would be admitting to a crime.