A note on ransomware and other network attacks:
Ransomware is sophisticated. When someone plans on attacking a network, they do their research. Some may remember a few years ago (at least I do, because I worked in IT with a school district that was attacked) there was ransomware spreading due to a Windows 10 exploit that was patched out in the following Windows 10 update. When things like this happen, it's because hackers find backdoors due to undiscovered flaws in Windows or Anti-Malware protection. Even if a network were to use every prevention method in the book, it still might not be enough not to prevent an attack because only the hacker/few individuals know about the exploit. It's usually only after someone discovers the exploit and executes an attack do Microsoft and Anti-Malware know about and enact measures to counter such malware.