While the Kremlin has denied the relationship between Moscow and the separatists, the emails show in great detail how Russia controlled virtually every detail of the separatist effort in the Russian-speaking regions of Ukraine, which has torn the country apart and led to a Russian takeover of Crimea.
And unlike the reported Russian hack of the Democratic National Committee, the Ukrainian hack reached deep into the office of the Russian president.
"This is a serious hack," said Maks Czuperski, head of the Digital Forensic Research Lab of the Atlantic Council (DFRL), which has searched through the email dump and placed selected emails on-line.
"We have seen so much happen to the United States, other countries at the hands of Russia," said Czuperski. "Not so much to Russia. It was only a question of time that some of the anonymous guys like Cyber Hunta would come to strike them back."
A senior U.S. intelligence official said the U.S. "had no role" in the hack.
Surkov has been a close aide to Putin for more than a decade, serving as both deputy prime minister and Putin's deputy chief of staff. The hacked emails date from 2014, a period during which Surkov was called the "gray cardinal" of the Kremlin, Putin's behind-the-scenes aide responsible for managing Russia's most crucial operations. He guided separatists not just in Ukraine, but in breakaway "republics" in Georgia as well.
It's as if the Russians were able to hack the email of Ben Rhodes, the deputy national security director and close aide to President Obama.
Specifically, the anonymous Ukrainian hackers were able to download the Outlook email accounts of Surkov's assistants, including a "Masha" and an "Yevgenia," according to the DFRL. Surkov himself apparently doesn't use email. The files included "the inbox, outbox, drafts, deleted email, spam, etc.," said Czuperski, noting 2,337 messages in total were dumped.
Emails from the Outlook accounts of Surkov's assistants by Digital Forensic Research Lab at the Atlantic CouncilA senior U.S. official, asked if the material was authentic, told NBC News that there was "nothing to indicate otherwise."
Hidden in the one gigabyte file are a variety of materials that provided evidence of Russian involvement at the highest levels in the war in eastern Ukraine, which has taken the lives of 10,000 people, including the 298 passengers and crew of Malaysian Flight 17, shot down by a separatist missile in July 2014 over Ukraine.
There is a list of casualties in the Donbass region of Ukraine sent from a high-ranking separatist official, and a list of candidates for office in a sham election. One email notes that the individuals with asterisks next to their name were "checked by us" and are "especially recommended." Days later, those same names were announced as having been "elected."
There are expense reports and a proposal for a government press office in Donetsk, scene of some of the fiercest fighting -- a three-person operation for separatist propaganda, with an editor, reporter and webmaster.
One U.S. official told NBC News that the material confirms much of what the U.S. believed was going on at the time, that the Kremlin was running the separatists at a micro-level. In fact, the official noted that Surkov's name was the first on a list of Russians and Ukrainians placed under executive sanctions by President Obama in March 2014, citing his role in the separatist movement. The action froze his U.S. assets in the United States and banned him from entering the country. Similar sanctions were imposed by the European Union.
Czuperski said he believed that since Russian authorities realized they were dealing with a violation of international law, they wanted to keep the details in their emails close-hold. He said that while he believes there is likely more hacked material, and that it may prove politically sensitive, he doesn't know that for sure, or whether "Cyber Hunta," like WikiLeaks, will continually dump material.
"It's all time and probability -- how much effort you put in and how much effort the adversary puts in," he said.
Robert Windrem, NBC News