- It was earlier estimated the data breach affected 50 million users
- Facebook has announced new privacy tools for its users
- Mark Zuckerberg will testify in Congress next week over data scandal
The new figure eclipses a previous estimate of 50 million in a further embarrassment to the social network roiled by a privacy scandal.
The announcement came as Facebook unveiled clearer terms of service to enable users to better understand data sharing, and as a congressional panel said chief executive Mark Zuckerberg would appear next week to address privacy issues.
Facebook's chief technology officer Mike Schroepfer released the new figures on affected users as he discussed implementation of new privacy tools for users of the huge social network.
"In total, we believe the Facebook information of up to 87 million people -- mostly in the US -- may have been improperly shared with Cambridge Analytica," he said.
The new estimate could deepen the crisis for Facebook, which has been pressured by the disclosures on hijacking of private data by the consulting group working for Donald Trump's 2016 campaign.
Schroepfer said new privacy tools, which had been announced last month, would be in place by next Monday.
"People will also be able to remove apps that they no longer want. As part of this process we will also tell people if their information may have been improperly shared with Cambridge Analytica," he said.
"Overall, we believe these changes will better protect people's information while still enabling developers to create useful experiences."
Zuckerberg on the Hill
Earlier Wednesday, the House of Representatives' Energy and Commerce Committee announced what appeared to be the first congressional appearance by Zuckerberg since the scandal broke on the hijacking of data on tens of millions of users.
The April 11 hearing will "be an important opportunity to shed light on critical consumer data privacy issues and help all Americans better understand what happens to their personal information online," said the committee's Republican chairman Greg Walden and ranking Democrat Frank Pallone in a statement.
"We appreciate Mr. Zuckerberg's willingness to testify before the committee, and we look forward to him answering our questions."
Zuckerberg will likely face multiple congressional hearings as his social media giant battles a firestorm following revelations that the British consulting firm Cambridge Analytica obtained the data of 50 million Facebook users to try and manipulate US voters in the 2016 presidential election.
His participation is yet unconfirmed but Senator Dianne Feinstein told the San Francisco Chronicle that Zuckerberg had agreed to attend that hearing.
Zuckerberg, who has been making a series of media appearances after staying silent for several days on the breach, said earlier this week it would take "a few years" to fix the problems uncovered by the revelations on data misuse.
He told Vox.com that one of Facebook's problems was that it was "idealistic," focusing on the positive aspects of connecting people and that "we didn't spend enough time investing in, or thinking through, some of the downside uses of the tools."
The world's biggest social network faces probes on both sides of the Atlantic over the misuse of data, which Facebook attributed to a breach of terms of service by an academic researcher linked to the consulting firm working for Donald Trump's campaign.
Deleting Russian 'trolls'
Late Tuesday, Facebook said it deleted dozens of accounts linked to a Russian-sponsored internet unit which has been accused of spreading propaganda and other divisive content in the United States and elsewhere.
The social networking giant said it revoked the accounts of 70 Facebook and 65 Instagram accounts, and removed 138 Facebook pages controlled by the Russia-based Internet Research Agency (IRA).
The agency has been called a "troll farm" due to its deceptive post aimed at sowing discord and propagating misinformation.
The unit "has repeatedly used complex networks of inauthentic accounts to deceive and manipulate people who use Facebook, including before, during and after the 2016 US presidential elections," said a statement Facebook chief security officer Alex Stamos.
Zuckerberg said in a separate statement on his Facebook page that the Russian group "has been using complex networks of fake accounts to deceive people."
He added: "While we respect people and governments sharing political views on Facebook, we do not allow them to set up fake accounts to do this. When an organization does this repeatedly, we take down all of their pages, including ones that may not be fake themselves."
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