Tech giants Facebook, Google, and Twitter testified for the first time to senators on Tuesday as part of an ongoing congressional investigation into Russian meddling in the 2016 election.

Representatives from the three tech titans spoke to what they know about alleged Russian interference using their platforms to buy ads, promote stories, and spread misinformation in an effort to influence the outcome of the election.

All three company representatives agreed with the intelligence community's assessment that the Kremlin was instrumental in launching propaganda operations against the US before and during the election period, they confirmed.

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One of the likely end-game outcomes for lawmakers is to push legislation, notably the Honest Ads Act, to increase advertising transparency to help counter the effects of foreign governments and so-called troll farms. That includes the notorious Kremlin-based Internet Research Agency (IRA), a key instrument used by the Russian state to spread fake and false content during the election, lawmakers contend.

That said, not one of the company representatives would say if they would support the newly created draft legislation.

Here's what we learned from Tuesday's hearing:

FACEBOOK SAYS OVER 126 MILLION PEOPLE SAW RUSSIAN-PRODUCED POSTS IN THE RUN-UP TO THE ELECTION

Colin Stretch, Facebook's general counsel, said 29 million US-based Facebook users were served ads and other promoted content to their news feed from the IRA.

That's almost three-fold on the original figure that Facebook provided Congress earlier this year.

But because these posts were shared and promoted, the company said as many as 126 million users may have seen the ads -- accounting for more than half of its US user base. Many of the ads and promoted content were on highly charged political topics relating to gun ownership and LGBTQ+ and racial issues. Facebook said in its testimony that the total number of those illegitimate ads are a drop in the ocean -- less than 0.004 percent of all content -- or about 1 in 23,000 news feed items. But Stretch conceded that "any amount is too much."

The company said it deleted around 170 accounts on Instagram, which it owns, accounting for about 120,000 posts.

TWITTER REVEALS THOUSANDS OF ACCOUNTS ASSOCIATED WITH RUSSIAN ELECTION MEDDLING

In his published testimony, Sean Edgett, Twitter's acting general counsel, confirmed that 2,752 accounts were associated with the IRA, up from the initially reported 201 accounts previously identified.

Twitter has faced criticism for claims that it was slow to respond to deleting accounts associated with Russian meddling, per reports. Edgett's testimony said that some of the accounts were known about as early as 2015. Sen. Mark Warner (D-VA) criticized the social media giant at the time for not conducting a thorough initial investigation.

Those 2,752 accounts have all since been suspended from the service, Twitter said.

Out of more than 16 billion tweets, the company said about 1.4 million automated, election-related tweets received about 288 million impressions. Twitter stressed that the figure was a small proportion of overall election-related tweets -- less than 1 percent.

FACEBOOK SAYS IT STOPPED RUSSIA-BACKED "APT28" HACKERS TARGETING US POLITICAL PARTY EMPLOYEES

Facebook also confirmed for the first time that APT28, a Russian intelligence agency-backed hacking group, was using the social platform in the run-up to the election in an effort to target employees of major US political parties.

"We warned the targets who were at highest risk, and were later in contact with law enforcement authorities about this activity," said Stretch.

The hacking group, also known as "Fancy Bear," is notorious for state-sponsored campaigns and political meddling as part of the Kremlin's cyber-espionage programs. The group is thought to be responsible for the attacks on the Democratic National Committee (DNC) during last year's election, which led to thousands of emails from the Clinton campaign to be leaked and published online.

FireEye earlier this year revealed several attacks attributed to the group, using malware to target specific groups or individuals.

The relevance is important. Microsoft earlier this year sued the hacking group in an evidently one-sided legal battle, and won. The action allowed the company to seize domain names used to impersonate Microsoft by the hackers to spread malware.

GOOGLE SAYS IT SAW ONLY "LIMITED ACTIVITY" FROM RUSSIAN MEDDLING, BUT VOWS TO DO BETTER

Google's published and spoken testimony pointed to "limited activity" by Russian propagandists on its network and services, according to the company's senior counsel, Richard Salgado.

The search giant said it conducted a broad review of its ads network -- its primary money-maker -- dating back to mid-2015, but only two accounts were identified as connected to Russia-backed entities. Google also said it found 18 channels on YouTube with 1,100 videos dedicated to political content, of which only a fraction had more than a few thousand views. Salgado said the videos weren't targeted at anyone in particular, but were shared on other social media platforms. Many of those social accounts were set up using Gmail, said Salgado.

Salgado promised that the company will release a transparency report regarding election ads on top of its existing government data demands and takedown request reports.

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