Sally Yates testifies before the Senate about Michael Flynn and Russia

Former acting Attorney General Sally Yates and former Director of National Intelligence James Clapper were interviewed by the Senate Judiciary subcommittee on crime and terrorism on Monday about Russia's interference in the 2016 election.

The subcommittee's chairman, Republican Sen. Lindsey Graham, said in his opening statement that "when one party is attacked, all of us should feel attacked ... when a foreign power interferes in our election, it doesn't matter who they targeted. We're all in the same boat."

Graham added that he is confident it was the Russians, and not "some 400-pound guy sitting on his bed," who hacked the Democratic National Committee and Hillary Clinton's campaign chairman, John Podesta, during the election.

Graham said he wants to learn more about the "unmasking" of US citizens like former national security adviser Michael Flynn, who may have been caught up, incidentally, in surveillance of monitored non-US persons believed to be foreign agents.

Democratic Sen. Sheldon Whitehouse, the ranking member of the subcommittee, outlined the threat Russia continues to pose to the US and President Donald Trump's ties to Russia in a lengthy opening statement.

"We need a more thorough accounting of the facts," Whitehouse said.

Clapper, the former Director of National Intelligence, said in his opening remarks that he "didn't expect to be before this Committee, or any other Committee in Congress, again so soon, since I thought I was all done with this when I left the government. But understandably, concern about the egregious Russian interference in our election process is so critically serious as to merit focus - hopefully bi-partisan focus - by Congress and the American people."

He went on to outline the process by which the intelligence community concluded in January that "the Russian government pursued a multi-faceted influence campaign in the run-up to the election, including aggressive use of cyber capabilities."

"The Intelligence Community Assessment concluded, first, that President Putin directed an influence campaign to erode the faith and confidence of the American people in our presidential election process. Second, that he did so to demean Secretary Clinton. And, third, that he sought to advantage Mr. Trump," Clapper said.

"The conclusions and confidence levels reached at the time still stand," he added.

Clapper also addressed the issue of the "unmasking" of US persons caught up in surveillance of monitored foreign agents - the process by which it was revealed that former national security adviser Michael Flynn had been speaking with Russia's ambassador to the US, Sergey Kislyak, during the presidential transition period.

"On several occasions during my six-and-a-half years as DNI, I requested the identity of U.S. persons to be revealed," Clapper said. "In each such instance, I made these requests so I could fully understand the context of the communication and the potential threat being posed. At no time did I ever submit a request for personal or political purposes, or to voyeuristically look at raw intelligence, nor am I aware of any instance of such abuse by anyone else."

He added, however, that leaks of this kind of information "is an unauthorized disclosure" that is "improper under any circumstance."

Yates, the former deputy attorney general who was fired by Trump in January after refusing to enforce his first immigration order, used her opening statement to outline her experience working in the Justice Department for 27 years "through five Democratic and Republican administrations." She emphasized that "the efforts by a foreign adversary to interfere with and undermine our democratic processes - and those of our allies - pose a serious threat to all Americans."

Yates said she intends for her "answers today to be as fulsome and comprehensive as possible while respecting my legal and ethical boundaries," but she is restrained by her "duty to protect classified information," which "applies just as much to me as a former official as it did when I led the department."

This story is being updated.