Neither the FBI, nor the NSA has been allowed to examine the server. The DNC has refused to allow ANYONE to examine it. Nor has it been kept in a secure location, so it is useless as evidence now.
We only have the word of the DNC that it was the “Russians” that did this.
Odd that, despite there being such an outcry that there was a crime committed the DNC refused to allow any investigation, innit?