SAN FRANCISCO (NYTIMES) - When Christine Blasey Ford testified before Congress last month about Justice Brett Kavanaugh's alleged sexual assault, a website called Right Wing News sprang into action on Facebook.

The conservative site, run by blogger John Hawkins, had created a series of Facebook pages and accounts over the last year under many names, according to Facebook.

After Dr Ford testified, Right Wing News posted several false stories about her - including the suggestion that her lawyers were being bribed by Democrats - and then used the network of Facebook pages and accounts to share the pieces so that they proliferated online quickly, social media researchers said.

The result was a real-time spreading of disinformation started by Americans, for Americans.

What Right Wing News did was part of a shift in the flow of online disinformation, falsehoods meant to mislead and inflame.

In 2016, before the presidential election, state-backed Russian operatives exploited Facebook and Twitter to sway voters in the United States with divisive messages.

Now, weeks before the midterm elections on Nov 6, such influence campaigns are increasingly a domestic phenomenon fomented by Americans on the left and the right.

"There are now well-developed networks of Americans targeting other Americans with purposefully designed manipulations," said Ms Molly McKew, an information warfare researcher at the New Media Frontier, a firm that studies social media.

Politics has always involved shadings of the truth via whisper campaigns, direct-mail operations and negative ads bordering on untrue.

What is different this time is how domestic sites are emulating the Russian strategy of 2016 by aggressively creating networks of Facebook pages and accounts - many of them fake - that make it appear as if the ideas they are promoting enjoy widespread popularity, researchers said. The activity is also happening on Twitter, they said.

The shift toward domestic disinformation raises potential free speech issues when Facebook and Twitter find and curtail such accounts that originate in the United States, an issue that may be sensitive before the midterms.

"These networks are trying to manipulate people by manufacturing consensus - that's crossing the line over free speech," said Mr Ryan Fox, a co-founder of New Knowledge, a firm that tracks disinformation.

This month, Twitter took down a network of 50 accounts that it said were being run by Americans posing as Republican state lawmakers. Twitter said the accounts were geared toward voters in all 50 states.

On Thursday (Oct 11), Facebook said it had identified 559 pages and 251 accounts run by Americans, many of which amplified false and misleading content in a coordinated fashion. The company said it would remove the pages and accounts.

Among them were Right Wing News, which had more than 3.1 million followers, and left-wing pages that included the Resistance and Reverb Press, which had 240,000 and 816,000 followers.

Facebook said this amounted to the most domestic pages and accounts it had ever removed related to influence campaigns. The company said it had discovered the activity as part of its broader effort to root out election interference.

Also, the pages had become more aggressive in using tactics like fake accounts and multiple pages to make themselves appear more popular.

"If you look at volume, the majority of the information operations we see are domestic actors," said Mr Nathaniel Gleicher, Facebook's head of security. He added that the company was struggling with taking down the domestic networks because of the blurry lines between free speech and disinformation.

Mr Gleicher said the accounts and pages that Facebook took down on Thursday violated its rules about online spam and that many of the domestic organisations probably had financial motivations for spreading disinformation.

The organisation can make money by getting people to click on links in Facebook that then direct users to websites filled with ads. Once someone visits the ad-filled website, those clicks means more ad revenue.

But while traditional spam networks typically use celebrity gossip or stories about natural disasters to get people to click on links that take them to ad-filled sites, these networks were now using political content to attract people's attention.

"Today, sensational political content seems to be a more effective way for people to build an audience for their pages and drive traffic to their websites, which earn them money for every visitor to the site," Mr Gleicher said.

Right Wing News did not return calls or e-mails seeking comment.

After this article was published online, Mr Hawkins tweeted, "I have not been involved with running the Right Wing News Facebook page this year. Additionally, I haven't created any fake accounts on Facebook."

Administrators for the Facebook page for the Resistance also did not respond to requests for comment.

Mr Ed Lynn, who runs Reverb Press, said he had no advance notice that Facebook would be removing the page.

"I believe Facebook has made a mistake where Reverb Press is concerned. We are a legitimate American news and opinion publication," Mr Lynn said in a statement. He said he was appealing Facebook's decision.

While domestic disinformation multiplies, foreign disinformation appears to be less prominent - or may be more hidden. That may be because Facebook and other social media companies have adopted measures to hunt for and remove foreign interference on their sites.

Those efforts are starting to show some results. In July, Facebook, Twitter and YouTube announced they had identified and eliminated a new Russian network aimed at influencing Americans before the midterms.

Domestic disinformation is harder to root out than foreign disinformation, researchers said, because in many cases it mirrors genuine networks of Americans engaging in free speech online.

Social media services can act to remove domestic disinformation only when the American groups that are making and distributing it start to use techniques that violate the companies' terms of service, such as creating false accounts.

"Facebook's tactics are extremely ineffective in stopping these networks of hundreds of Facebook pages and accounts from spreading disinformation," said Ms Natalie Martinez, a fellow at Media Matters, a nonprofit in Washington that monitors disinformation from conservative American sites.

"Ultimately, if you are a US national and you decide to share something, the social networks have no reason to stop you."

Ms Martinez said Facebooks actions against Right Wing News and other domestic disinformation networks would stem some of the flow of false content - but only for a little while.

"There is little to stop them from spawning off as a new page, or account, and just starting to build their network again," she said. "They can just keep trying to get around Facebook's rules."