Comment by GVIrish

It's not about whether someone is a contractor or a full time government employee. Contractors work on the government site just as much as FTE's, receive the same security training, and are indoctrinated into the same culture.

The problem is inadequate access control to classified materials. There tends to be a lot of information that people can access without a need to know, that is not rigorously tracked and locked down. This means that someone looking to steal or leak can get their hands on a lot of stuff they shouldn't without raising suspicions if they're not stupid about it.

The reason we may be seeing a number of spillage incidents with contractors is simply because there a lot of contractors working at government agencies. In IT a lot of the time contractors outnumber government people by a significant margin.