(CBS) — Facebook and Twitter executives are defending their companies in two congressional hearings, arguing they are aggressively trying to root out malicious foreign actors who want to do the United States harm just weeks before the midterm elections.

Google declined to send a top executive, so the company’s absence is marked by a glass of water and empty chair in the hearing room.

Both Senate Intelligence Committee Richard Burr, R-North Carolina, and Vice Chairman Mark Warner, D-Virginia, both lambasted Google for failing to sent a top representative.

Burr emphasized that the platforms have significant influence in shaping the nation’s conversation, and even left the possibility of further regulation open.

“What is under attack is the idea that business as usual is good enough,” Burr said in his opening statement. “The information that your platform disseminates changes minds.”

Twitter’s CEO Jack Dorsey faces some angry Republicans who claim his platform is biased against conservatives.

In prepared testimony released ahead of a House hearing Wednesday afternoon, Dorsey says his company does not use political ideology to make decisions, and aims to make as many voices heard as possible.

But that, according to some, is a part of the problem.

Twitter has been criticized for allowing conspiracy theorist Alex Jones to remain on the the platform, even after accusing victims of the Sandy Hook and Parkland shootings of being crisis actors.

Jones showed up to the hearing Wednesday.

Sen. Martin Heinrich asked Sandberg if claiming shooting victims are crisis actors violates company’s standards, but Heinrich did not demand and answer from Dorsey.

On the issue of foreign influence, Sandberg said Russian interference, “violated the values of our company, and of the country we love,” and emphasized that Facebook is increasing its staffing to identify malicious actors.

“These are expensive investments, but that will not stop us because we know they are critical, she said.

Congress has sharply criticized the social media companies over the last year as it has become clear that they were at the forefront of Russia’s interference in the 2016 elections and beyond. That scrutiny has led to additional criticism over the companies’ respect for user privacy and whether conservatives are being censored — frustrations that are particularly heightened ahead of the midterms.

In her testimony, Sandberg detailed ongoing efforts to take down material linked to the Russian agency, including the removal this year of 270 Facebook pages.

Still, Sandberg says the company’s overall understanding of the Russian activity in 2016 is limited “because we do not have access to the information or investigative tools” that the U.S. government has.

“This is an arms race, and that means we need to be ever more vigilant,” Sandberg says. Sandberg’s mea culpa, however, appears to mirror that of Facebook CEO Mark Zuckerberg, whose appearance before Capitol Hill in April was widely panned by lawmakers as a glorified apology tour.

“We didn’t take a broad enough view of our responsibility, and that was a big mistake, and it was my mistake, and I’m sorry,” Zuckerberg told lawmakers at the time.

Dorsey meanwhile says Twitter has continued to identify accounts that may be linked to the same Russian internet agency in Mueller’s indictment.

He says Twitter has so far suspended 3,843 accounts the company believes are linked to the agency, and has seen recent activity.

The afternoon hearing in the House Energy and Commerce Committee will feature only Dorsey in a hearing focused on bias and the platform’s algorithms.

Some Republicans, including President Trump, have pushed the idea ahead of the elections that Twitter is “shadow banning” some in the GOP because of the ways search results have appeared. Twitter denies that is happening.

To address the concerns, Dorsey offers an explanation of how Twitter uses “behavioral signals,” such as the way accounts interact and behave on the service. Those signals can help weed out spam and abuse. He says such behavioral analysis “does not consider in any way” political views or ideology.

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