The U.S. has formally blamed Russia for recent political hacking attacks, saying they were "intended to interfere with the U.S. election process."
U.S. intelligence officials said they are "confident" that the Russian government directed those attacks on American political organizations, the Department of Homeland Security and the Office of the Director of National Intelligence on Election Security said Friday in a joint statement.
"The recent disclosures of alleged hacked e-mails on sites like DCLeaks.com and WikiLeaks and by the Guccifer 2.0 online persona are consistent with the methods and motivations of Russian-directed efforts," the agencies said.
Kremlin spokesman Dmitry Peskov said the U.S. accusations that Russia is behind these cyberattacks are "nonsense," Interfax reported. The spokesman said "tens of thousands of hackers" attack Russian President Vladimir Putin's site "every day."
"Many attacks are traced to US territory. But we're not blaming the White House or Langley every time," he said.
Washington was able to determine Russia's involvement based on the "signature" of the attacks, which a government official told NBC News hackers may not have realized they left behind. The official used an analogy of a criminal investigation of a home invasion: the Russians might "shimmy down the chimney," the Chinese "would kick the door down" and the North Koreans "would build a tunnel and flood the chamber."
Rep. Adam Schiff, D-Calif., commended the decision to name Russia and called for a more coordination with European allies that "deters further meddling."
"All of us should be gravely concerned when a foreign power like Russia seeks to undermine our democratic institutions, and we must do everything in our power to guard against it," said Schiff, a ranking member of the House Permanent Select Committee on Intelligence.
Sen. Dianne Feinstein, D-Calif., vice chairman of the Senate Intelligence Committee said the Russian hacking of the U.S. election system is "intolerable" and that the U.S. needs to develop a strong response.
Sen. Cory Gardner, R-Colo., said the Obama administration's "strategic patience policy has failed" and that he plans to introduce a bill that would impose sanctions on Russia's cyber criminals. The bill would resemble similar provisions within the North Korea Sanctions and Policy Enhancement Act.
"Russia's interference with American democracy is a direct threat to our political process, and it may only be the tip of the iceberg. It is imperative that Russia's behavior is met with strength in the form of aggressive sanctions to show the world that its cybercrimes will not be tolerated," said Gardner, chairman of the Senate Foreign Relations Subcommittee on East Asia, the Pacific, and International Cybersecurity.
Friday's news comes after thousands of internal emails between Democratic officials were dumped by WikiLeaks ahead of the party's national convention this summer.
Last month, Putin called the hacking of Democratic National Committee emails a public service, but denied accusations that his government was involved in the email hack.
"The important thing is the content that was given to the public," he said in an interview with Bloomberg.
Putin denied the allegations despite U.S. officials and cybersecurity experts pointing to evidence that Russia was behind the security breach that resulted in the release of thousands of emails.
While this activity is "not new to Moscow," the U.S. intelligence community and Department of Homeland Security said it would be "extremely difficult" for hackers to actually "alter ballot counts or election results," because of the "decentralized nature" of the U.S. election system and the "number of protections state and local election officials have in place."
The Department of Homeland Security, however, urged election officials to remain vigilant and ask for cybersecurity assistance if needed.
"I don't know if we know it was Russia who broke into the DNC," the Republican presidential candidate said when the first presidential debate turned to the topic of cybersecurity. "She keeps saying 'Russia, Russia, Russia,' and maybe it was. It could be Russia but it could be China, could also be lots of other people. It could be someone sitting on their bed that weighs 400 pounds."
Tensions between the United States and Russia have been high since Moscow annexed Crimea in 2014. And in more recent months, representatives for President Barack Obama and Putin have struggled to coordinate efforts in Syria, resulting in increased tensions.
In September, Secretary of State John Kerry announced an agreement with Russia in an attempt to implement a nationwide cease-fire in the war-torn country. Kerry, at the time, called the deal a potential "turning point" in the Syrian conflict.
But the State Department said Monday that Russia did not hold up its end of an agreement. The Kremlin has similarly blamed the U.S. for the collapse of the deal and strongly cautioned the U.S. against carrying out attacks on Syrian government forces.
— NBC News' Bob Windrem, Kelly O'Donnell, Tracy Snyder and Alexey Eremenko contributed to this report.