If I were to join the military right now wanting to work on computer systems, how long would it take before I'm actually preforming that role, or would they have to "break" me first? Hackers have no desire to do that when they can easily stay in the private sector and earn twice the pay and have a nice cushy office to work out of.
There should be some kind of alternate route to joining the military for officer and specialization roles (in my opinion of course, I am certainly interested to here if anyone has objections). Give me a few tests, an interview, a basic physical, a polygraph, and some IT training to get familiar with the systems and let me go to work. High pay isn't really an issue for me personally as long as I enjoy the work and am constantly learning or teaching.
Having access to that information is a huge responsibility. There have been spies at all ranks that have done large amounts of harm to the US military. It is absolutely necessary to lock down machines and have strict security checks over each other a logging of everything.