Facebook CEO Mark Zuckerberg began the two-day testimony before the US congressional senate committee with another public apology Tuesday. But it did not help him much as senators grilled him with uncomfortable questions on the company's dubious privacy regulations that led to the Cambridge Analytica fiasco.

Among several senators, Kamala Harris (D-CA) came down heavily on Zuckerberg. She was particularly concerned on how Facebook values trust and why the social media firm wasn't transparent enough to loyal users. 

Harris questioned Zuckerberg on when he personally got to know about the data breach and discussions among senior executives to come out clean by informing Facebook users.

Zuckerberg replied that he became aware of the issue in 2015. The company had held several meetings and an immediate decision was taken to ban Kogan and Cambridge Analytica from accessing Facebook data. They were also told to delete all the user information with a third-party certification.

Facebook CEO
Facebook CEO Mark Zuckerberg admits to erring in not informing users about the data leakReuters

Believing that both the guilty parties had erased the data, Facebook decided not to inform the users, as it was a closed chapter. But, as it turned out, Cambridge Analytica lied to Facebook.

Zuckerberg finally admitted to Harris that blindly trusting Cambridge Analytica's word on deleting illegally stashed user data was a big mistake.

Day one of the testimony has concluded but will continue Wednesday and we expect more details from Zuckerberg on the action taken by the company on the data breach.

Facebook recently made several changes to its privacy guidelines for both users and third-party app developers.

Facebook data leak backstory:

Aleksandr Kogan, a Cambridge University researcher, had conducted what looked like a harmless survey through a personality testing app — This Is Your Digital Life — on Facebook in 2014.

Apparently, 30 million people showed interest in the testing app and voluntarily shared their personal data and Facebook friends' personal information. But, Kogan, unwittingly thinking it's legal, shared close to 87 million user data to data mining company Cambridge Analytica.

Cambridge Analytica used the data to illegally create 'psychographic' profiles and delivered the content online.

This was a crooked method to trick citizens to believe a particular candidate (their client) is good, while the rival is evil, thereby swinging a political election.

It is believed that Donald Trump's campaign team had hired the services of Cambridge Analytica during the 2016 US presidential election.

Cambridge Analytica is accused of manipulating citizens to vote for their client while creating vile online content to malign opposition candidates in elections.

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