Facebook's Zuckerberg contrite ahead of grilling in Congress

In prepared remarks released by a congressional panel, Zuckerberg admitted he was too idealistic and failed to grasp how the platform -- used by two billion people -- could be abused and manipulated.

The 33-year-old is to testify before senators on Tuesday and House lawmakers on Wednesday amid a firestorm over the hijacking of data on millions of Facebook users by the British firm Cambridge Analytica, which worked with Donald Trump's campaign.

"We didn't take a broad enough view of our responsibility, and that was a big mistake. It was my mistake, and I'm sorry," Zuckerberg said in his written testimony released by the House commerce committee.

"I started Facebook, I run it, and I'm responsible for what happens here."

In his written remarks, Zuckerberg called Facebook "an idealistic and optimistic company" and said: "We focused on all the good that connecting people can bring."

But he acknowledged that "it's clear now that we didn't do enough to prevent these tools from being used for harm as well. That goes for fake news, foreign interference in elections, and hate speech, as well as developers and data privacy."

- Investigating every app -

Zuckerberg recounted a list of steps announced by Facebook aimed at averting a repeat of the improper use of data by third parties like Cambridge Analytica, and noted that other applications were also being investigated to determine if they did anything wrong.

"We're in the process of investigating every app that had access to a large amount of information before we locked down our platform in 2014," said Zuckerberg, who was seen Monday on Capitol Hill, where he had at least one private meeting with a lawmaker.

"If we detect suspicious activity, we'll do a full forensic audit. And if we find that someone is improperly using data, we'll ban them and tell everyone affected."

Facebook has taken a series of proactive steps to make up for massive lapses in protecting personal data, as lawmakers signaled they intend to get tough on privacy.

Last week, the company announced new privacy tools to be in place in user news feeds on Monday, and said it would notify the 87 million users affected by the data hijacking scandal, amid probes underway on both sides of the Atlantic.

Over the weekend, it said it had suspended another data analysis firm, US-based Cubeyou, after reports that it had used private data harvested from psychological testing apps for commercial purposes.

- Backing 'Honest Ads' -

On Friday, Facebook sought to quell some concerns over political manipulation of its platform by announcing support for the "Honest Ads Act" that requires election ad buyers to be identified, and to go further with verification of sponsors of ads on key public policy issues.

Zuckerberg said the change will mean "we will hire thousands of more people" to get the new system in place ahead of US midterm elections in November.

"We're starting this in the US and expanding to the rest of the world in the coming months," Zuckerberg said.

On Monday, Facebook also agreed to supply proprietary data for a study on its role in elections and democracy, researchers announced.

"In consultation with the foundations funding the initiative, Facebook will invite respected academic experts to form a commission which will then develop a research agenda about the impact of social media on society -- starting with elections," a company statement said.

"The focus will be entirely forward looking. And our goals are to understand Facebook's impact on upcoming elections -- like Brazil, India, Mexico and the US midterms -- and to inform our future product and policy decisions."

Facebook has said it has seen little impact on its business from the privacy scandal despite a #deleteFacebook movement and concerns from advertisers.

But Brian Wieser of Pivotal Research said the entire digital advertising industry, of which Google and Facebook are the leaders, could be impacted by the scandal.

The changes announced by Facebook and Google restricting third-party access "indicate a higher likelihood that both companies will 'raise their walls' ... Both of these trends will likely harm ad tech companies focused on buying media or otherwise focused on the Facebook and Google ecosystems."

One prominent tech leader, Apple co-founder Steve Wozniak, announced meanwhile that he was leaving the social network.

"Users provide every detail of their life to Facebook," Wozniak told USA Today.

"Facebook makes a lot of advertising money off this. The profits are all based on the user's info, but the users get none of the profits back."