"We believe that we have a responsibility to prevent the misuse of our platforms and we take that very seriously", said Walker, who has previously testified before the committee and was the official Google hoped to send again.
Sandberg, in her prepared remarks, detailed how Facebook was addressing the problem but reiterated that the company was slow to spot it.
Twitter isn't biased for or against any type of partisan but is working on ways to raise the level of debate on its platform, the company's CEO will tell a Senate hearing in Washington, D.C., today.
The Senate Intelligence Committee has been looking into efforts to influence USA public opinion for more than a year, after United States intelligence agencies concluded that Kremlin-backed entities sought to boost Republican President Donald Trump's chances of winning the White House in 2016.
Senator Richard Burr, the committee's Republican chairman, said he expected the hearing would focus on solutions to the problem of foreign efforts to influence U.S. elections and sow political discord, with a jab at Google.
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"I'm skeptical that, ultimately, you'll be able to truly address this challenge on your own", he told the hearing with Dorsey and Facebook chief operating officer Sheryl Sandberg. "We are learning from what happened, and we are improving". Earlier this year Facebook founder and CEO Mark Zuckerberg testified before lawmakers in part to explain how the personal information of tens of millions of Facebook users ended up in the hands of the United Kingdom -based data firm Cambridge Analytica.
Dorsey will then participate in a second hearing Wednesday afternoon before the House Energy & Commerce Committee, where he is set to discuss the algorithms Twitter uses to serve content on users' Twitter feeds and "content monitoring".
The companies have made many policy changes, and have caught and banned malicious accounts over the past year. Twitter denies that's happening.
"What I hope to see from the two executives who are appearing before the committee is a similar seriousness and transparency and a focus on recognizing that while they may have taken steps, this is an ongoing problem and much remains to be done", Rosenberger said.