Hacking can leave traces.
Servers have root logs that are not publicly known.
Actually, secure servers are behind a DMZ and are firewalled.
It's very possible that these political party servers were not secured properly.
Never heard of a private VPN with signed certificates?
You have been watching too many movies
Sounds more plausible that there are moles or someone sold out ...
4 years of hearings and investigations -- LMAO ...
Trump isn't even inaugurated and in office and the investigations are beginning .. Enjoy the shit-storm ...