Russia has become the latest target of email hackers, according to an NBC report.
A Ukrainian group called Cyber Hunta has released more than a gigabyte of emails and other materials from the office of one of Russian President Vladimir Putin's top aides, Vladislav Surkov.
Dating back to 2014, the emails show Russia's involvement with the separatist movement in Ukraine. The separatist effort in the Russian-speaking regions of Ukraine was responsible for the rift in the country and the eventual takeover of Crimea by Russia.
"This is a serious hack," said Maks Czuperski, head of the Digital Forensic Research Lab of the Atlantic Council (DFRL).
"We have seen so much happen to the United States, other countries at the hands of Russia. Not so much to Russia," Czuperski continued. "It was only a question of time that some of the anonymous guys like Cyber Hunta would come to strike them back."
The emails provide evidence of Russia's involvement at the highest levels in the war in eastern Ukraine, which has killed 10,000 people, including the 298 passengers aboard the Malaysian Flight 17 that was shot by a missile in July 2014 over Ukraine.
A U.S. official told NBC News that the evidence confirms what the U.S. already believed: that the Kremlin was running the separatist movement.
Surkov's name was the first on a list of Russians and Ukrainians placed under executive sanctions by President Barack Obama in March 2014, citing his role in the separatist movement. The action froze his assets in the United States and banned him from entering the country.
A senior U.S. intelligence official said the U.S. "had no role" in the hack.