Facebook believes the data of up to 87 million people was improperly shared with the political consultancy Cambridge Analytica – many more than previously disclosed.
The overall figure had been previously quoted as being 50 million by the whistleblower Christopher Wylie.
Facebook chief Mark Zuckerberg said “clearly we should have done more, and we will going forward”.During a press conference he said that he had previously assumed that if Facebook gave people tools, it was largely their responsibility to decide how to use them.
But he added that it was “wrong in retrospect” to have had such a limited view.
“Today, given what we know… I think we understand that we need to take a broader view of our responsibility,” he said.
As a result, many people’s public profile information had been “scraped” and matched to the contact details, which had been obtained from elsewhere.
Facebook has now blocked the facility.
“It is reasonable to expect that if you had that [default] setting turned on, that in the last several years someone has probably accessed your public information in this way,” Mr Zuckerberg said.
What is the controversy about?
Facebook has faced intense criticism after it emerged that it had known for years that Cambridge Analytica had collected data from millions of its users, but had relied on the London-based firm to self-certify that it had deleted the information.
Cambridge Analytica: The story so far Cambridge Analytica said it had bought the information from the creator of the This Is Your Digital Life app without knowing that it had been obtained improperly.
The firm says it deleted all the data as soon as it was made aware of the circumstances.
But Channel 4 News has since reported that at least some of the data in question is still in circulation despite Cambridge Analytica insisting it had destroyed the material.
During Mr Zuckerberg’s press conference, Cambridge Analytica tweeted it had only obtained data for 30 million individuals – not 87 million – from the app’s creator, and again insisted it had deleted all records.
Facebook’s share price has dropped sharply in the weeks since the allegations emerged.
In his Wednesday blog post, Mr Schroepfer detailed new steps being taken by Facebook in the wake of the scandal.
Mr Zuckerberg now regrets saying it was a “pretty crazy idea” that fake news on Facebook could have helped Donald Trump become president When asked about this by the BBC, he said he had decided that his chief technology officer and chief product officer should answer questions from countries other than the US.
He added, however, that he had made a mistake in 2016 by dismissing the notion that fake news had influenced the US Presidential election.
“People will analyse the actual impact of this for a long time to come,” he added.
“But what I think is clear at this point is that it was too flippant and I should never have referred to it as crazy.”