The company has been struggling for months to address the steadily mounting evidence that Russians manipulated the social media platform in their bid to tip the presidential election in favor of Republican Donald Trump.
Democratic lawmakers in recent days had demanded that Facebook be more open about what it knows and to dig more deeply into its troves of data to analyze the propaganda effort, which the company has acknowledged involved at least 470 fake accounts and pages created by a shadowy Russian company that spent more than $100,000 targeting U.S. voters. Lawmakers particularly wanted copies of the ads bought through the fake accounts, some of which Facebook officials showed to Hill investigators and then took away, making further study impossible. The company said sharing the ads would compromise users' privacy.
Facebook chief executive Mark Zuckerberg announced a reversal of that decision Thursday, saying that the company believed it could share the ads with Congress without compromising user privacy. The company already had shared at least some of the same information with special counsel Robert S. Mueller III.
"I care deeply about the democratic process and protecting its integrity," Zuckerberg said on Facebook Live, a video streaming service provided by the company. "Facebook's mission is all about giving people a voice and bringing people closer together. Those are deeply democratic values, and we're proud of them. I don't want anyone to use our tools to undermine democracy. That's not what we stand for."
The company has been slow to respond to signs, dating to November, that Russians used Facebook and other technology platforms to deliver propaganda and manipulate voter sentiment. As evidence has grown, including from Facebook's internal investigations, lawmakers have pushed the company and others to search more deeply and more quickly for answers — both to determine what happened in 2016 and to head off a repeat in future elections.
Hill investigators are still seeking a longer, more-detailed version of an investigative report into election meddling on the platform that Facebook concluded in April. A 13-page final version was released publicly that month but without many of the details included in earlier drafts, which were several times longer, say people familiar with the investigation. The public report made no explicit mention of Russia, nor did it discuss the possibility that the propaganda may have included messages delivered through advertising — the core of Facebook's multibillion-dollar business.
The steps Zuckerberg announced Thursday — which included efforts to improve the review of political ads and enhance transparency about who buys them — drew some praise from lawmakers who recently had expressed frustration with the company.
"This is an iconic company in many ways, but they really rely on the trust of their users. I think the steps they took today were important and necessary. But there are still a lot of questions." said Sen. Mark R. Warner (D-Va.), the highest-ranking Democrat on the Senate Intelligence Committee.
Warner said he believes the full impact of the 470 fake Russian accounts and pages remains unknown and probably has been played down by Facebook. He said more than 3,000 ads could have reached tens of thousands of users through their Facebook "friends," causing a dramatic influence on voting narrowly won by Trump in several states. Warner said Facebook still needs to do more intense investigation into other ways that its platform was manipulated.
"Americans ought to be able to see the content of ads that are used for and against candidates," Warner said. "Americans both need to know what happened in the election of 2016, and have confidence going forward that if they see an ad it isn't sponsored by a foreign government."
His House Intelligence Committee counterpart, Rep. Adam B. Schiff (D-Calif.), said in a statement: "The data Facebook will now turn over to the Committee should help us better understand what happened, beyond the preliminary briefings we already received. It will be important for the Committee to scrutinize how rigorous Facebook's internal investigation has been, to test its conclusions and to understand why it took as long as it did to discover the Russian sponsored advertisements and what else may yet be uncovered."
Republicans on the committee did not have any immediate comment.
The halting response from Facebook has resulted from a combination of pressures on Zuckerberg, who has been reluctant to impose restrictions on users' free speech but also have come to accept that stronger measures are necessary against abuse, say people familiar with his thinking.
"What we're seeing is Mark's idealism coming up against the hard realization that they were hacked in this way that nobody was expecting," said Tim O'Reilly, chief executive of Silicon Valley publisher O'Reilly Media. "He is acknowledging that online media enables targeting in ways that are impossible for broadcast media to do — so the tools of disclosure need to actually be more transparent."
Facebook is not alone in drawing the attention of investigators. U.S. intelligence agencies have portrayed a broad propaganda campaign by the Russians, and numerous independent researchers have detailed evidence of propaganda flowing through Google, Twitter and other tech platforms. Lawmakers have called for their full cooperation and made clear that tech executives should be prepared to testify before investigative committees on Capitol Hill.
But Facebook has drawn particular attention in the weeks since it announced, on Sept. 6, that the Internet Research Agency, a notorious troll farm based in St. Petersburg, Russia, had purchased political ads through Facebook.
Zuckerberg, in his remarks, also vowed to continue investigating and cooperating with federal authorities, including on unanswered questions involving the possible involvement of other Russian groups and those in former Soviet states. Facebook will begin requiring that political ads make clear what accounts have bought them and also what other ads the account is running elsewhere on the social media platform, Zuckerberg said.
The company also plans to expand its team working on election integrity and build better connections with electoral officials in many nations.
"We are in a new world," Zuckerberg said. "It is a new challenge for internet communities to deal with nation states attempting to subvert elections. But if that's what we must do, we are committed to rising to the occasion."
Tom Hamburger and Dana Priest contributed to this report.
Follow The Post's tech blog, The Switch, where technology and policy connect.