The Daily Beast has the details:
The hacker who claims to have stolen emails from the Democratic National Committee and provided them to WikiLeaks is actually an agent of the Russian government and part of an orchestrated attempt to influence U.S. media coverage surrounding the presidential election, a security research group concluded on Tuesday.
The researchers, at Arlington, Va.-based ThreatConnect, traced the self-described Romanian hacker Guccifer 2.0 back to an Internet server in Russia and to a digital address that has been linked in the past to Russian online scams. Far from being a singly, sophisticated hacker, Guccifer 2.0 is more likely a collection of people from the propaganda arm of the Russian government meant to deflect attention away from Moscow as the force behind the DNC hacks and leaks of emails, the researchers found.
ThreatConnect is the first known group of experts to link the self-proclaimed hacker to a Russian operation, amidst an ongoing FBI investigation and a presidential campaign rocked by the release of DNC emails that have embarrassed senior party leaders and inflamed intraparty tensions turning the Democratic National Convention. The emails revealed that party insiders plotted ways to undermine Sen. Bernie Sanders’ presidential bid.
WikiLeaks hasn't responded to Guccifer 2.0’s claims of responsibility for the email leak.