1) It's using a SMBv1 exploit, which can be done via LAN or via Internet if ports are open. Security Roll Up from March will fix it, there is also a specific release for other unsupported OSes like XP/8 & Server 2003. Disabling SMBv1 should also work.

2) Only in WINE and you'll have to run it yourself.

3) Partly NSA for weaponizing the exploit. Users for not updating. Hackers/Crackers for creating it.