WannaCrypt-like SMB spreading technique was widely used in Stuxnet, as docummented by Symantec and Kaspersky.
Read this: W32.Stuxnet Dossier (2010,Symantec PDF)
Now we have the name of the exploit: EternalBlue
It is pretty disingenuous for Microsoft to blame the NSA when they have known about it for this long.
So Microsoft reacted within 2 days to close the barn door, and has released patches for all previous Windows versions from XP through 8.
Microsoft Customer Guidance for WannaCrypt attacks (5/12/17, MS TechNet)
Now just ask yourself, how did Microsoft so miraculously come up with these multiple patches for this diverse group of operating systems, in time to release them on Sunday, Mother's Day, unless they were hoarding them themselves?
They released some to extended customers but not all. Selective pay-for-play.
While Microsoft griped about NSA exploit stockpiles, it stockpiled patches: Friday's WinXP fix was built in February - "It took three months to release despite Eternalblue leak."
I will give them credit for building the fix into Windows 10.
My question is: What is different now?
Sub-question: Are we to believe that we can trust Microsoft in the future? I certainly can understand paying extra for patches like this, but the fact that they kept them secret begs the question of their trustworthiness.