U.S. officials are publicly blaming the Russian government for several high-profile hacks against political groups that they claim were meant to interfere with the upcoming election.
U.S. intelligence agencies are confident Russia was responsible, the Department of Homeland Security and the Office of the Director of National Intelligence said in a statement on Friday.
They allege that the Russian government compromised the emails of U.S. officials and institutions and then publicly leaked them online through sites such as WikiLeaks, DCLeaks, and the anonymous hacker Guccifer 2.0, who took credit for breaching the Democratic National Committee earlier this year.
"These thefts and disclosures are intended to interfere with the U.S. election process," the statement said.
Although the agencies didn't provide specific evidence, they said the "methods and motivations" behind the hacks were consistent with Russian-directed efforts.
"Such activity is not new to Moscow — the Russians have used similar tactics and techniques across Europe and Eurasia, for example, to influence public opinion there," the statement said.
The agencies also said that only Russia's senior-most officials could have authorized these attacks.
The Russian Embassy didn't immediately respond to a request for comment. But the country's government has repeatedly denied any involvement with the hacks.
Perhaps the most serious of those breaches was at the Democratic National Committee. In June, it reported that suspected hackers had stolen sensitive files from the group, including opposition research on presidential candidate Donald Trump.
A hacker calling himself Guccifer 2.0, along with WikiLeaks, later posted those files online.
In another serious hack in September, stolen emails from former Secretary of State Colin Powell were published online through a site called DCLeaks.
Security experts have suspected that the incidents may all be part of a Russian-sponsored campaign to shape media coverage of the U.S. election and damage Democrat Hillary Clinton's election chances for president.
U.S. intelligence officials privately believed that Russia was in some way involved, but officially nothing was said until Friday.
The intelligence agencies also said some U.S. states had recently experienced the "scanning and probing" of their election-related systems from servers operated by a Russian company.
"However, we are not now in a position to attribute this activity to the Russian Government," Friday's statement said.
DHS is urging state and local election officials to be vigilant and ask for cybersecurity assistance. Several states have already done so. But the agencies also said that hacking U.S. election systems would be difficult, given that they are distributed across 50 states and that protections are already in place.