Hari Sreenivasan: What role did social media play in Russian efforts to influence the 2016 U.S. presidential election? We now know fake accounts created by Moscow reached more Americans than the total number of U.S. citizens who voted.

For the record, the NewsHour has worked with both Facebook and Twitter. The three tech giants were back on Capitol Hill today. Appearing before two separate congressional Intelligence Committees, Facebook, Twitter and Google lawyers faced tougher questions than yesterday.

First, at the Senate Intelligence Committee, the Democrat from California, Dianne Feinstein–

Sen. Dianne Feinstein:I must say, I don't think you get it, that what we're talking about is a cataclysmic change. What we're talking about is the beginning of cyber-warfare. We are not going to go away, gentleman. And this is a very big deal.

Hari Sreenivasan: Yesterday, Facebook admitted that from June 2015 to August 2017, 120 fake Russian accounts posted 80,000 times and reached as many as 126 million Americans.

That number was revised to nearly 150 million today, as 16 million more people were reached by Russian Instagram posts. All three companies admitted fault again. Facebook's general counsel, Colin Stretch...

Colin Stretch: The fact that foreign actors were able to use our platform to exploit that openness is a deeply painful lesson for us, and one we're focused on learning from going forward.

Hari Sreenivasan: The representatives vowed to invest more money, time and people to do better. At times, lawmakers used the hearing to draw partisan lines on Russia's impact on the election. Republican from Florida Marco Rubio:

Sen. Marco Rubio: These operations, they're much more widespread than one election. And it's about our general political climate. Is that correct?

Colin Stretch: I would certainly agree with that statement, Senator.

Hari Sreenivasan: Democratic Senator from New Mexico Martin Heinrich:

Sen. Martin Heinrich: Last month, President Trump called Russian-purchased Facebook ads a hoax. Are they, in fact, a hoax?

Colin Stretch: No. The existence of those ads were on Facebook, and wasn't a hoax.

Hari Sreenivasan: The House Intelligence Committee released dozens of those ads, some exhibited with blown-up versions. Lawmakers chided Facebook for their existence.

All of the ads focused on hot-button, divisive issues, one for an event called — quote — "Down With Hillary" by the group Being Patriotic, another mirroring the social movement Black Lives Matter.

Back on the Senate side, Twitter was singled out multiple times. The Republican Senator from Arkansas Tom Cotton questioned where Twitter's loyalties lie.

Sen. Tom Cotton: Is it biased to side with America over our adversaries?

Sean Edgett: We are trying to be unbiased around the world.

Hari Sreenivasan: Top Democrat on the Senate Committee Mark Warner expressed doubt over Twitters' claim that it found only about 2,800 accounts linked to Russian operatives.

Sen. Mark Warner: I'm concerned, sir, that Twitter seems to be vastly underestimating the number of fake accounts and bots pushing disinformation. Independent researchers, people who have testified before this committee, have estimated that up to 15 percent of active Twitter accounts, or potentially 45 million-plus accounts, are fake or automated.

Hari Sreenivasan: Representatives from each company said none has yet to identify the full scope of Russian interference on their platforms.