Sheryl Sandberg, Facebook's chief operating officer, and Jack Dorsey, Twitter's chief executive officer, are scheduled to answer questions on Wednesday from the Senate Intelligence Committee in what is the most anticipated hearing on technology since April when Facebook CEO Mark Zuckerberg testified before two Congressional committees.
The committee also invited a senior executive from Google, but the company has not committed to sending Google CEO Sundar Pichai or Alphabet CEO Larry Page.
Sandberg is expected to detail Facebook's efforts to fight misinformation and manipulation, pointing out that the company has doubled the number of people it has working on safety and security, according to her written testimony.
"We have more than doubled the number of people working on safety and security and now have over 20,000. We review reports in over 50 languages, 24 hours a day," Sandberg wrote in testimony provided by Facebook ahead of a Wednesday hearing with the Senate Intelligence Committee.
"Better machine learning technology and artificial intelligence have also enabled us to be much more proactive in identifying abuse," the testimony said.
Globally, Facebook had disabled 1.27 billion fake accounts from October 2017 to March 2018, according to the testimony.
"We're getting better at finding and combating our adversaries, from financially motivated troll farms to sophisticated military intelligence operations," Sandberg's testimony said.
Facebook knows it "can't stop interference by ourselves," Sandberg's testimony said. "We don't have all the investigative tools that the government has, and we can't always attribute attacks or identify motives."
Facebook, Twitter and Google continue to face questions over just what they're doing to stop foreign interference in upcoming elections, as well as broader questions about their efforts to minimize harassment on their platforms. The companies are also under fire from some on the right who believe the companies have shown liberal bias and are censoring conservative views.
"These two companies don't really have many public friends in Congress right now, instead on both sides they've got multiple partisan battles to fight," said Dipayan Ghosh, a fellow at the Harvard Kennedy School's Shorenstein Center and a former privacy and public policy advisor at Facebook.
"The Senate is going to be asking some pretty serious questions of both Dorsey and Sandberg as to what exactly their current practice is, what they discovered and what they think Congress should do or the U.S. government should do going forward to more effectively police these platforms," he added.
Sen. Mark Warner, D-Va., who is vice chairman of the Senate Select Committee on Intelligence, said in a statement to NBC News that the hearing would be focused on the future and not looking backward at election interference in the 2016 presidential election.
"I've told the companies that I am not looking for this hearing to be a retrospective on what happened in 2016," he said. "I want to know, one, what they're doing to prevent this happening in 2018 and beyond; and two, I want to have a conversation about policy solutions."
He added that last month he put out a paper with some ideas for regulation and wanted to hear from the companies "what ideas they think make sense, which ones don't, and other ideas they might have to combat misinformation, protect consumer data and privacy, and promote competition in this space."
Twitter did not immediately reply to request for comment.
Testimony released by the House of Representatives ahead of another hearing Dorsey will have in Washington on Wednesday showed the Twitter CEO planned to address censorship concerns upfront.
"Twitter does not use political ideology to make any decisions, whether related to ranking content on our service or how we enforce our rules," according to testimony Dorsey is expected to give to the House Committee on Energy and Commerce. "We do not shadowban anyone based on political ideology."
Google declined to confirm if it would have anyone in person at the hearing, but said Kent Walker, it's senior vice president of global affairs and chief legal officer, will be in Washington and will deliver written testimony.
In the testimony, Walker states that Google remained deeply concerned about attempts to undermine democratic elections and had rolled out several changes designed to increase transparency in election advertising and to improve election cybersecurity.
The hearing comes after theSenate heard from third-party social media experts last month who said Russia and other foreign actors showed few signs of slowing their efforts to spread misinformation and propaganda, and that tech companies were not doing enough to stop those efforts.
"We are constantly looking to find signals that help us identify deceptive content, while promoting content that is authoritative, relevant, and current," Walker said in the testimony.
Justin Brookman, the director of consumer privacy and technology policy at Consumers Union, the nonprofit publisher of Consumer Reports, said social companies do not have the appropriate level of artificial intelligence technology or staff to combat misinformation or election interference for the massive number of users across their platforms.
"They have very few content moderators historically," said Brookman, who is also a former policy director for the FTC's Office of Technology Research and Investigation. "There's been pressure on them to start cracking down on some of this stuff since 2016, but it's really hard to do them at scale."
"How to do you address it when it's not that hard to set up 50,000 fake Twitter accounts and to buy lots of followers?" he said. "How do you prevent those abuses? It's hard, but important."