Cyber warfare is being conducted as a never-ending swordfight between black and white hats. Will the white hats ever suggest that they need to be made obsolete? Of course not! Even though they are well-intentioned and very talented engineers, they rely on the existence of both the black hats and the inherent software vulnerabilities. But if vendors can download software over the Internet, so can hackers. A computer does not have to be built this way. Instead, it can be constructed so that no software can ever be downloaded over the Internet. The Navy still has a few examples of a very old computing machine, the AN/YUK-7 (on Flight II Ticonderoga-class cruisers), that exhibits the solution.
The machine has two completely separate banks of magnetic core memory: one with the executable program code that is run on its central processing unit, and another that contains the data the program will use to make its computations as it runs. This was done to make it twice as fast, since it was a very slow memory architecture.