Facebook's Mark Zuckerberg meets Shimon Peres
Facebook's Mark Zuckerberg meets Shimon Peres Flash 90

Facebook CEO Mark Zuckerberg on at a Wednesday press conference told reporters that he will not step down after the Cambridge Analytica affair.

He also noted that up to 87 million Facebook accounts may have been compromised, and it is not yet clear how much data Cambridge Analytica and app designer Aleksandr Kogan obtained.

"We don't know how many people's data Kogan got and what he sold to Cambridge Analytica," Zuckerberg admitted, adding that he was "confident" the number was no more than 87 million, and that it could be less.

According to allegations, in 2014, the UK-based firm Cambridge Analytica gained access to the personal data of some 50 million Facebook users, taking advantage of a loophole in the system which permitted a personality quiz application to gain access not only to the data of the 270,000 users who took the quiz, but all of their Facebook friends’ accounts as well.

The data had been sold to Cambridge Analytica by the author of the quiz, University of Cambridge academic Aleksandr Kogan. Cambridge Analytica then used the data to engage in “micro-targeting” for clients, mining a wealth of personal information to determine which users are most receptive to particular messages.

Zuckerberg also admitted that Facebook "didn't take a broad enough view" of what their responsibility was. "That was a huge mistake, that was my mistake," he added.

"At the end of the day, this is my responsibility," Zuckerberg admitted. "I started this place, I run it, I am responsible for what happens here. I'm not looking to throw anyone else under the bus."

However, he said he was "not aware" of a consideration by Facebook's board to remove him, and said he believes he is the best person to run the company.

"My hope is by the end of this year, we’ll have turned a corner on a lot of these issues and people see things are getting a lot better," he said.

Zuckerberg will testify before Congress next week.