SAN FRANCISCO — In 2014, Russians working for a shadowy firm called the Internet Research Agency started gathering American followers in online groups focused on issues like religion and immigration. Around mid-2015, the Russians began buying digital ads to spread their messages. A year later, they tapped their followers to help organize political rallies across the United States.
Their digital instrument of choice for all of these actions? Facebook and its photo-sharing site Instagram.
The social network, more than any other technology tool, was singled out on Friday by the Justice Department when prosecutors charged 13 Russians and three companies for executing a scheme to subvert the 2016 election and support Donald J. Trump’s presidential campaign. In a 37-page indictment, officials detailed how the Russians repeatedly turned to Facebook and Instagram, often using stolen identities to pose as Americans, to sow discord among the electorate by creating Facebook groups, distributing divisive ads and posting inflammatory images.
While the indictment did not charge Facebook, it provided the first comprehensive account from the authorities of how critical the company’s platforms had been to the Russian campaign to disrupt the 2016 election. Facebook and Instagram were mentioned 41 times, while other technology that the Russians used were featured far less. Twitter was referenced nine times, YouTube once, and electronic payments company PayPal 11 times.
It is unprecedented for an American technology company to be so central to what the authorities say was a foreign scheme to commit election fraud in the United States. The indictment further batters Facebook’s image after it has spent months grappling with questions about how it was misused and why it did not act earlier to prevent that activity.
Jonathan Albright, research director at Columbia University’s Tow Center for Digital Journalism, said the indictment laid bare how effectively Facebook could be turned against the country.
“Facebook built incredibly effective tools which let Russia profile citizens here in the U.S. and figure out how to manipulate us,” Mr. Albright said. “Facebook, essentially, gave them everything they needed.” He added that many of the tools that the Russians used, including those that allow ads to be targeted and that show how widespread an ad becomes, still pervade Facebook.
Facebook, with more than two billion members on the social network alone, has long struggled with what its sites show and the kind of illicit activity it may enable, from selling unlicensed guns to broadcasting live killings. The company’s business depends on people being highly engaged with what is posted on its sites, which in turn helps make it a marquee destination for advertisers.
When suggestions first arose after the 2016 election that Facebook may have influenced the outcome, Mark Zuckerberg, the company’s chief executive, dismissed the concerns. But by last September, Facebook had disclosed that the Internet Research Agency had bought divisive ads on hot-button issues through the company. It later said 150 million Americans had seen the Russian propaganda on the social network and Instagram.
The resulting firestorm has damaged Facebook’s reputation. Company officials, along with executives from Google and YouTube, were grilled by lawmakers last fall. Facebook has since hired thousands of people to help monitor content and has worked with Robert S. Mueller III, the special counsel leading the investigation into Russian election interference. It has also changed its advertising policy so that any ad that mentions a candidate’s name goes through a more stringent vetting process. Mr. Zuckerberg has vowed to not let Facebook be abused by bad actors.
Yet Facebook’s multiple mentions in Friday’s indictment renew questions of why the world’s biggest social media company didn’t catch the Russian activity earlier or do more to stop it. How effective the company’s new efforts to reduce foreign manipulation have been is also unclear.
In Silicon Valley, where Facebook has its headquarters, some critics pilloried the company after the indictment became public.
“Mueller’s indictment underscores the central role of Facebook and other platforms in the Russian interference in 2016,” said Roger McNamee, a Silicon Valley venture capitalist who had invested early in Facebook. “In its heyday, television brought the country together, giving viewers a shared set of facts and experiences. Facebook does just the opposite, enabling every user to have a unique set of facts, driving the country apart for profit.
Joel Kaplan, Facebook’s vice president of global policy, said in a statement that the company was grateful the government was taking action “against those who abused our service and exploited the openness of our democratic process.”
He added that Facebook was working with the Federal Bureau of Investigation ahead of this year’s midterm elections to ensure that a similar manipulation campaign would not take place. “We know we have more to do to prevent against future attacks,” he said.
Facebook has previously questioned whether law enforcement should be more involved in helping to stop the threat from nation state actors. Facebook said it worked closely with the special counsel’s investigation.
YouTube did not respond to a request for comment, while Twitter declined to comment. PayPal said in a statement that it has worked closely with law enforcement and “is intensely focused on combating and preventing the illicit use of our services.”
According to the indictment, the Internet Research Agency, created in 2014 in St. Petersburg and employing about 80 people, was given the job of interfering with elections and political processes.
The group began using American social media to achieve those aims in 2014, when it started making Facebook pages dedicated to social issues like race and religion. Over the next two years, the indictment said, the Russians stole the identities of real Americans to create fake personas and fake accounts on social media. The group then used those to populate and promote Facebook pages like United Muslims of America, Blacktivist and Secured Borders.
By 2016, the indictment said, the size of some of these Russian-controlled Facebook groups had ballooned to hundreds of thousands of followers.
The Russians then used these groups to push various messages, including telling Americans not to vote in the 2016 election for either Mr. Trump or his opponent, Hillary Clinton. In October 2016, according to the indictment, one Russian-controlled Instagram account called Woke Blacks posted a message saying: “Hatred for Trump is misleading the people and forcing Blacks to vote Killary. We cannot resort to the lesser of two devils. Then we’d surely be better off without voting AT ALL.”
Around 2015, according to the indictment, the Russians also started purchasing ads on Facebook and other social media sites like Twitter, targeting specific communities within the United States. The group used stolen PayPal accounts to pay for the ads and to promote posts, spending hundreds of thousands of dollars on the outreach.
In one ad, published to promote a Facebook event called “Down with Hillary,” an image of Mrs. Clinton was shown with a black “X” painted across her face. The text read, “Hillary Clinton is the co-author of Obama’s anti-police and anti-Constitutional propaganda.”
By mid-2016, according to the indictment, the Russians were using their fake Facebook personas to organize political rallies in the United States. That June, for example, posing as the United Muslims of America on Facebook, they promoted a rally called “Support Hillary. Save American Muslims.” For an August 2016 event organized through Facebook, the Russians also paid for a cage to be built that was large enough to hold an actress depicting Mrs. Clinton in a prison uniform.
At every step, the Russians used Facebook’s own tools to make sure their propaganda was as effective as possible. Those tools allowed them to get real-time results on which types of ad campaigns were reaching their target audience or which posts were getting the most engagement with viewers.
Researchers said that those tools are still widely available and that while the company has worked to remove fake accounts and stem the flow of disinformation, it has refused to let outside researchers examine the data on how Russian actors used the platform so effectively.
“They’re taking steps to fix this, but there’s no easy solution,” Anton Vuljaj, a Republican media strategist who has advised campaigns and media groups, said of Facebook and other social media companies. “This also shows that the public needs to be more vigilant about what is real and what is not online.”