Windows, Windows, Windows!
Why not become the first large company not to use any Microsoft products, and see what happens?
If this came out of North Korea it is a government Ordered attack.
That means that it was something that someone in power wanted done.
If they want it done resource would be directed to figure out how to do it. Every operating system has flaws. Those ordered to attack the company would do the necessary research to find an exploitable flaw.