Business Insider reports on a jailed hacker claiming to have breached the DNC as part of a Russian-led intelligence operation:

A Russian hacker believed to be a member of a hacking collective called Lurk said in court over the summer that he was ordered by Russia’s security services, known as the FSB, to hack the Democratic National Committee.

The hacker, Konstantin Kozlovsky, told a Moscow court in August of this year that his nine-member hacking group – which has been accused of stealing over $17 million from Russia’s largest financial institutions since 2013 – has been cooperating with the FSB for several years, according to the independent Russian news outlet The Bell. Part of that cooperation included hacking the DNC, he said.

Kozlovsky said during a hearing on August 15 that he “performed various tasks under the supervision of FSB officers,” including a DNC hack and cyberattacks on “very serious military enterprises of the United States and other organizations.”

Doubtful this is legit, but even if it is not, I think it is safe to say the Russians are responsible for the DNC breach and other recent similar attacks.