The firm's former employee Christopher Wylie accused Cambridge Analytica of gathering the details of Facebook through a personality quiz in 2014. All opinions expressed are those of the authors.

Senator John Kennedy (R- LA) was a little more blunt than some of his colleagues today in conveying certain issues to Mark Zuckerberg. "We have many systems in place to prevent the sale of illegal goods, and do not allow ads around the sale of endangered animals", Facebook said in a statement.

Mark Zuckerberg's appearance on Capitol Hill transfixed social media. He was respectful to a fault, beginning nearly every response with the title "Senator".

"We were slow to identify the [Russian] disinformation operations", he said. With apps, Facebook isn't selling data - it's giving the data to apps for free.

"I am very committed to making sure Facebook is a platform for all ideas", Zuckerberg responded.

"Wrap it up, Grandpa Grassley", tweeted one user to the Judiciary Committee chairman, who was deep into his first term in the Senate when Zuckerberg was born in 1984. And then he cracked his first smile of the day. Johnson's questioning can be found here and below. At that point, the company's market cap was $561 billion; at Tuesday's market close, Facebook's market cap was $479.4 billion, according to Bloomberg.

Facebook's CEO spent five hours on Tuesday alternately answering and deflecting questions about user privacy and how the social network handles your data.

The Dow Jones Industrial Average rose 1.8 per cent to end the day at 24,408.00, while the broad-based S&P 500 advanced 1.7 per cent to 2,656.87. In Peters's case, the question happened to refer to one of the biggest conspiracy theories that people believe about Facebook. Facebook attempts to police content that can cause "real-world harm", such as terrorism, self-harm, or election interference, according to Zuckerberg. Confusing terms of service written in hard-to-understand language obscure the true nature of the agreement.

He later told Sen.

Another advisable option is Privacy Badger by the non-profit Electronic Frontier Foundation. Cornyn said apologies are "not enough" and suggested legislation could eventually be needed to give consumers more control over their data privacy. Cantwell fired a series of questions related to Palantir and its relationship to Facebook. And it was my mistake, and I'm sorry. Richard Blumenthal, D-Connecticut, whose aides displayed an enlarged section of the Terms of Service for "This Is Your Digital Life" app. The text made clear that collected user data might be sold or passed along to third parties.

Wearing a dark suit and tie instead of his typical T-shirt and jeans, Zuckerberg remained largely unruffled and serious as senators questioned him. But he admits the technology has its limitations.

"Today, Mark Zuckerberg confirmed that Russian troll farms reached 126 million Facebook users".

He outlined steps the company has taken to restrict outsiders' access to people's personal information. He also needs to welcome regulation that Facebook can live with, including by offering fuller disclosure of political ads, without opening the company to further regulations.