From what I have researched, the only real breaches were to the Democratic party network and there information. I am not a proponent of trump but I am just not seeing where the breach took place, no one has produced any fake votes or voter fraud that could be traced to Moscow. If this was a cyber attack (which I believe it was) it was for the purpose of indirectly affecting the election by revealing damaging information. For instance, the revealing of emails that were erased, brought Clinton’s credibility into question. The exposure of Clinton having an private sever in her home with classified documents did more to damage her reputation than anything else. The most effective way to defend against hacking in this way is to not do stupid things like having classified documents on laptops and following the law which dictated that Clinton should not have had this server to begin with. To me best practices with passwords and network security is the best way to defend against attacks.
I agree access is necessary and is also the issue when policies are not enforced to govern access. In the case of Clinton and the server, there should have been some form of oversight that would not have allowed emails to be shared on this type of server. It is possible to control email access from a server and to restrict where emails are sent. I have to wonder why this was not done, you would think there would be much more control over the information flow.