Guccifer 2.0 is a persona which claimed to be the hacker(s) who gained unauthorized access to the Democratic National Committee (DNC) computer network and then leaked its documents to the media, WikiLeaks, and a conference event. The U.S. Intelligence Community accused Russian intelligence of the hacks and of operating the Guccifer 2.0 persona, which Guccifer 2.0 denied. There is wide media consensus in the west that Guccifer 2.0 was Russian, based partially on analysis from CrowdStrike, Fidelis Cybersecurity, FireEye's Mandiant, SecureWorks, ThreatConnect, Trend Micro, and the security editor for Ars Technica. WikiLeaks founder Julian Assange said multiple parties had access to DNC emails and that there was "no proof" Russia was behind the attack. The Department of Justice later 12 Russian Intelligence officers for the hack.
Thus Spake Guccifer 2.0 transcript