On their second day in Capitol Hill, lawyers from Facebook, Twitter, and Google took a bipartisan beating as they faced tough questions about the role their platforms played in Russian attempts to divide the American electorate. Members of the Senate Intelligence Committee grilled the tech executives about their responses to Russian interference in the 2016 election, arguing that the companies are not taking seriously what Congress considers a kind of cyberwarfare. Moreover, some members said the companies’ business models are built to enable the kind of disinformation campaigns Russians used to sow discord.

"Russians have been conducting information warfare for decades," said Democratic Sen. Mark Warner in his opening remarks. "But what is new is the advent of social-media tools with the power to magnify propaganda and fake news on a scale that was unimaginable back in the days of the Berlin Wall. Today’s tools seem almost purpose-built for Russian disinformation techniques."

The hearing revealed new and startling insight into the ways in which Russians pitted Americans against each other, and reinforced the notion that social-media ads are only a portion of the threat from foreign actors. Senators also forced the tech execs to explain how they police content on their platforms in different parts of the world.

Here were the most revealing exchanges.

"It's hard to attend an event in Houston, Texas when you're trolling from St. Petersburg, Russia." - Republican Sen. Richard Burr

Burr, the committee chair, highlighted two Facebook posts from a Russian propaganda group called Internet Research Agency that created a conflict on the streets of Houston by drawing two groups of protestors to fake “rallies” at the same place and time. One post, shared by the fake Facebook page Heart of Texas, promoted a purported protest against the "Islamization of Texas." The second post, uploaded by the fake page United Muslims of America, promoted an event aimed at saving "Islamic knowledge." Both groups bought ads to publicize their events, spending about $200 in total.

Burr then showed images of the resulting clash outside the Islamic Center in Houston, dramatizing how fake accounts can produce real conflict. Skeptics of the impact of Russian meddling in the US election have argued that just because Russia endeavored to influence American voters doesn't mean they did. But the fact that people showed up for these protests, designed to foment anger on both sides, demonstrates that influence.

"Do you believe that any of your companies have identified the full scope of Russian active measures?" - Warner

"I have to say no." – Facebook General Counsel Colin Stretch

In September, Facebook acknowledged that it had discovered 3,000 ads from 470 accounts connected to Internet Research Agency. It's since revealed that those accounts collectively created 80,000 pieces of content that may have been shared, both organically and through ads, with 126 million people. It shared that information with Twitter and Google. Now Twitter says it has identified 2,752 accounts linked to Internet Research Agency, while Google says it has identified 18 YouTube channels connected to the group.

But Warner said he’s concerned that much of what we know about Russian actions on these platforms is "derivative" of Facebook's initial findings. In response to his question, executives of Twitter and Google also said they did not believe their companies had yet uncovered the full extent of Russian activities.

The dialogue illustrates an important point: The companies have been slow to investigate and respond to Russian meddling, which started in 2015, more than two years ago. "Many of us on this committee have been raising these issues since the beginning of this year," Warner said. "Our claims were frankly blown off by the leadership of your companies."

"Is a foreign influence campaign a violation of the terms of service of any of the three companies represented here today?" - Republican Sen. Marco Rubio.