Facebook admits 2 billion users may have had their security breached

Facebook founder and CEO Mark Zuckerberg.

Facebook has admitted that the personal data of most of its 2 billion users may have been compromised - new evidence that the social network has failed to keep its security in check despite raking in billions of dollars in advertising revenue.

Facebook said it has removed a feature that allowed users to enter phone numbers or email addresses into the Facebook search bar to find other users. Facebook said the feature had been abused by bad actors to collect user information on their public personal profiles.

"Given the scale and sophistication of the activity we saw, we believe most people on Facebook likely had their profiles compromised in this way," Facebook said. "That's why we've now removed this feature."

Facebook also said that data from about 87 million users, mostly in the US, may have fallen into the hands of research firm Cambridge Analytica. This is the first time Facebook has officially confirmed the scale of the data leak, and the figure is much larger than the initial estimate of about 50 million users whose data was compromised.

"We didn't take a broad enough view of our responsibility, and that was a big mistake. It was my fault," Facebook CEO Mark Zuckerberg said on a call with reporters. "We're broadening our view of our responsibility."

Facebook has admitted that the personal data of most of its 2 billion users may have been compromised - fresh evidence of its security failures.

Mr Zuckerberg defended Facebook’s advertising business model and said he wanted to stay on as CEO of the company. He also said that a campaign by some users to delete their accounts on the social network had had little impact.

Facebook said it will notify individual users, through a notification at the top of their news feeds starting April 9, about whether their information may have been shared with Cambridge Analytica.

The US Congress said on April 4 that Mr. Zuckerberg will testify on April 9-10.

Facebook shares fell just over 1% in trading on Thursday, and were up more than 3% after the market closed. Since the Cambridge Analytica scandal broke, Facebook shares have fallen more than 16%.

Cambridge Analytica is a London-based political consulting firm that worked for Republican candidate Donald Trump’s 2016 US presidential campaign. The firm has been implicated in election manipulation in many countries around the world.

Cambridge Analytica's collection of Facebook user data is believed to have aimed to determine the tendencies of American voters, thereby trying to help Mr. Trump win.