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Alphabet, Facebook and Twitter have been summoned to appear before U.S. lawmakers once again, this time to answer for the extremist, terrorist content that appears on their sites.

The fresh round of scrutiny comes from the powerful Senate Commerce Committee, which oversees tech and telecom giants. The panel has scheduled a new Jan. 17 hearing to “examine the steps social media platforms are taking to combat the spread of extremist propaganda over the Internet,” its leader, Republican Sen. John Thune, announced Tuesday.

To many in Congress, tech giants in Silicon Valley have failed to fully thwart extremist groups like the Islamic State, which at times have spread terrorist propaganda and sought to recruit new followers using major international social media channels.

But this Senate hearing also threatens to expose Alphabet, Facebook and Twitter in particular to fresh questions about their handling of other hateful, conspiratorial or abusive content on their platforms — from racism and fake news to the rise of the alt-right.

So, too, is it bound to bring about more criticism of the tech industry’s handling of the 2016 election, when Russian-aligned trolls spread disinformation on social media in a bid to stoke political discord — content that reached hundreds of millions of web users.

Representing Facebook at the upcoming hearing will be Monika Bickert, the company’s Global Policy Management; Twitter is sending Carlos Monje, its director of public policy and philanthropy; and from Alphabet, the parent company of Google, it’ll be Juniper Downs, the global head of public policy and government relations with YouTube.

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