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Facebook and Twitter say they're trying their best to stop bad behavior on their sites. But Congress says it's not good enough anymore.

Two years after Russian influence campaigns swarmed the internet, using the world's largest social media companies as platforms to spread disinformation and interfere in the 2016 presidential election in the US, lawmakers say they're prepared to take action.

In a Washington, DC, hearing held Wednesday by the Senate Select Committee on Intelligence, senators pushed Facebook COO Sheryl Sandberg and Twitter CEO Jack Dorsey about why their businesses run the way they do. (Larry Page, CEO of Google parent Alphabet, was also invited to the hearing, but he declined to appear.) The lawmakers also asked what the companies are doing to reduce the effect of internet trolls, false stories and provocateurs who incite violence.

"I'm skeptical that, ultimately, you'll be able to truly address this challenge on your own," Virginia Sen. Mark Warner said during the hearing. "The era of the wild west in social media is coming to an end."

The hearing comes five months after Facebook CEO Mark Zuckerberg traveled to Capitol Hill to testify before three committees over two days about Cambridge Analytica, Russian election interference, and censorship.

The seriousness of Wednesday's hearing was clear from the start. Both Sandberg and Dorsey testified under oath, something Zuckerberg didn't have to do in April, and both were immediately peppered with questions around transparency, advertising and how the companies are trying to stop bad behavior.

Both Sandberg and Dorsey told the committees they've come to realize their respective companies were slow to react to the issues they now face daily, a feeling similar to one expressed by Zuckerberg in April. "We were too slow to spot this and too slow to act," Sandberg said. "That's on us."

Dorsey said the "required changes won't be fast or easy" but said he shared Sandberg's commitment to finding solutions.

Livestream

The drama wasn't just about the testimony. The conspiracy theorist Alex Jones, known for harassing parents of children who died in school shootings, by claiming those events were fakes and hoaxes, was also present at the hearings. Jones had traveled from his offices in Texas to, he said in a livestream rant from outside the hearing room, "face his accusers" after being banned by Facebook, Twitter, Google's YouTube and other services last month.

"They demonize me at these hearings and tell lies about me and I never get to face my accusers," he told CNET in an interview outside the hearing room, calling the hearing members "absolute cowards." He also got in a heated exchange with Sen. Marco Rubio outside the hearing room during a break. "I'm going to start showing up at these things," Jones said.

Continued election interference

The title for the Senate hearing was "Foreign influence operations and their use of social media platforms," which makes sense considering the committee is still investigating Russian interference in the 2016 presidential election. That -- and the fact that tech companies have already identified and shut down hundreds of accounts attempting to interfere with this year's US midterm elections, set for Nov. 6 -- means there's likely a lot to talk about.

"We have learned about how vulnerable social media is to corruption and misuse," said Senate intelligence committee Chairman Richard Burr. "The very worst examples of this are absolutely chilling, and a threat to our democracy."

But the questions weren't focused on just those topics. Lawmakers asked about everything from data collection practices to transparency reports.

Sen. Kamala Harris, for example, asked about Facebook's policies on hate speech, and why it seems to allow users to disparage black children but not white men. Sen. Angus King, meanwhile, asked about the threat of deepfakes, or videos and audio that've been altered by a computer program to convincingly change what people are saying and doing.

Now playing: Watch this: Silicon Valley is in the Capitol Hill hot seat again

Censorship question

As tech companies step up their efforts to fight election interference and false news, lawmakers and pundits have raised concerns that the firms have begun censoring conservative voices.

It's an issue that members of the House of Representatives Energy and Commerce Committee are likely to bring up in the committee's planned hearing with Dorsey shortly after the Senate hearing concludes Wednesday.

Rep. Greg Walden, the House committee's chairman, said questions about censorship are important to raise as these companies amass aggregate user bases larger than most countries, giving them extraordinary power over the flow of information.

"A lot of people are wondering, who's behind the curtain? And how is this being decided as to whose voice is heard first and whose voice is heard most," Walden, a Republican from Oregon, said in an interview Tuesday. "They don't have this right yet."

First published Aug. 30, 5 a.m. PT.

Updates, Sept. 5 at 5 a.m.: Adds details about viewing Wednesday's hearing; 6:42 a.m.: Includes details from opening remarks; 7:30 a.m.: Adds information about initial questions, and updates throughout; 7:41 a.m.: Includes details about conspiracy theorist Alex Jones attending the briefing; 8:57 a.m.: Adds further details about questions posed to companies; 9:43 a.m.: Includes more details about Sandberg's and Dorsey's testimony.

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