The Facebook founder apologised for the Cambridge Analytica (CA) data leak and promised to investigate ‘tens of thousands’ of apps to discover if any other companies have accessed data in a similar way.
And after a torrid few weeks for the social network, share price investors rewarded Mr Zuckerberg for appearing in Capitol Hill.
Facebook stocks rose 4.5% on Tuesday – which is said to have boosted the entrepreneur’s fortune by around £2.1bn.
Facebook says it is in the process of letting up to 87 million users know that their information may have been accessed by CA, and Mr Zuckerberg repeated his admission that the company ‘didn’t do enough’ to stop its tools ‘being used for harm’.
He also said the company was in an ‘arms race’ with Russia, warning there were people in the country tasked with finding ways to breach Facebook’s systems.
Speaking to the Senate Judiciary and Commerce Committees, the tech entrepreneur apologised that Facebook had not taken a ‘broad enough view’ of its responsibility for people’s public information.
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He said in a prepared statement: ‘It was my mistake, and I’m sorry. I started Facebook, I run it, and I’m responsible for what happens here.’
Mr Zuckerberg said its audit of third-party apps would highlight any misuse of personal information, and said the company would alert users instantly if it ‘found anything suspicious’.
When asked why the company did not immediately alert the 87 million users whose data may have been accessed by CA when first told about the ‘improper’ usage in 2015, Mr Zuckerberg said Facebook considered it a ‘closed case’ after CA said it had deleted it.
Mr Zuckerberg said: ‘In retrospect it was clearly a mistake to believe them.’
On the subject of fake news, Mr Zuckerberg said ‘one of my greatest regrets in running the company’ was its slowness at uncovering and acting against disinformation campaigns by Russian trolls during the US election.
He said the Russian campaign of disinformation had been discovered ‘right around the time’ of the US presidential election, and said the company had developed ‘new AI tools’ to identify fake accounts responsible.
He added: ‘You know there are people in Russia whose job is to exploit our systems… so this is an arms race.
‘They are going to keep getting better at this and we need to invest in keeping on getting better at this too..
Facebook and CA face multiple lawsuits over alleged misuse of personal information with at least five law firms in the UK and US investigating claims for compensation.
Culture Secretary Matt Hancock will meet Facebook representatives in London on Wednesday.