Mark Zuckerberg has revealed Facebook has been cooperating with the special prosecutor’s investigation into Moscow’s alleged election meddling, as he claimed countering Russian interference was “an arms race”.

Appearing before politicians on Capitol Hill for the first of two days of testimony, the Facebook CEO said the company he established in 2004 was seeking to undergo a “philosophical change” amid recent controversy over the inappropriate use of people’s data, even as he sought to shape any pending regulation.

Indeed, on a day that bore with it potentially huge implications for a $80bn company and its 33-year-old chief, Mr Zuckerberg seemed largely untroubled by the questions he encountered. Many commentators on social media suggested most of the senators questioning the Harvard drop-out, did no more than confirm how little they knew about the subject.

Senator John Thune, the Republican chairman of the Commerce Committee, told Mr Zuckerberg his company had a 14-year history of apologising for “ill-advised decisions” related to user privacy. He asked: “How is today’s apology different.”

Mr Zuckerberg, whose arrival on Capitol Hill was met by protesters outside the buildings in Washington DC, said: “We have made a lot of mistakes in running the company. I think it’s pretty much impossible, I believe, to start a company in your dorm room and then grow it to be at the scale that we’re at now without making some mistakes.”

The Facebook founder, dressed for once in a suit, white shirt and blue tie, had been reluctant to appear before the members of the Senate Judiciary and Commerce committees.

Yet, he was obliged to do so as controversy continued to swirl over the inappropriate harvesting of the data of an estimated 87m Facebook users by British political consulting firm Cambridge Analytica, who were accused of using that information to help Donald Trump’s election campaign. The company has denied that.

On Tuesday, Mr Zuckerberg told senators it had been “clearly a mistake” to believe Cambridge Analytica had discarded data that it had harvested from social media users in an attempt to sway 2016 elections.

According to the Associated Press, he told told senators Facebook considered the data collection “a closed case” because it thought the information had been deleted. Facebook did not alert the Federal Trade Commission, Mr Zuckerberg said, and he assured senators the company would handle the situation differently in the future.

Mr Zuckerberg, who hired outside consultants and a law firm to help him prepare for the session, was also asked if his company had been contacted by the office of the Special Counsel, Robert Mueller, who is looking into alleged Russian interference in the election and possible collision with the Trump campaign.

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He said he had not personally been questioned by Mr Mueller, but said other people from the company had been. He said he did not want to reveal any confidential information in public, but added: “I know that we are working with them.”

Earlier this year, Mr Mueller charged 13 Russian individuals and three Russian companies in a plot to interfere in the presidential election through a social media propaganda effort that included online ad purchases using US aliases and politicking on US soil. Some of the Russian ads were on Facebook.

Mr Zuckerberg said he considered the failure to promptly identify Russian efforts to interfere in the 2016 election was “one of biggest regrets in running the company”. He said methods to spread political misinformation would keep evolving and that the company was constantly strengthening its use of artificial intelligence and adding new employees to try to identify when the platform was being used maliciously.

How to stop Facebook from revealing everything about you Show all 9 1 /9 How to stop Facebook from revealing everything about you How to stop Facebook from revealing everything about you Lock your profile down If you haven’t done this already, do it now. In Settings, hit the Privacy tab. From here, you can control who gets to see your future posts and friends list. Choose from Public, Friends, Only Me and Custom in the dropdown menu. How to stop Facebook from revealing everything about you Limit old posts Annoyingly, changing this has no effect on who’s able to see your past Facebook posts. Instead, on the Privacy page, you have to click on Limit Past Posts, then select Limit Old Posts and finally hit Confirm on the pop-up. How to stop Facebook from revealing everything about you Make yourself harder to find You can stop completely random people from adding you by selecting Friends of Friends from the dropdown menu in the Who can send you friend requests? section of the Privacy page. It’s also worth limiting who can find your Facebook profile with your number and email address. At the bottom of the page is the option to prevent search engines outside of Facebook from linking to your profile. How to stop Facebook from revealing everything about you Control access to your Timeline You can limit who gets to post things on your Timeline and who gets to see posts on your Timeline too. In Settings, go to Timeline and Tagging and edit the sections you want to lock down. How to stop Facebook from revealing everything about you Block people When you block someone, they won’t be able to see things you post on your Timeline, tag you, invite you to events or groups, start conversations with you or add you as a friend. To do it, go to Settings and Blocking. Annoyingly, you have to block people on Messenger separately. You can also add friends to your Restricted list here, which means they’ll still be friends with you but will only be able to see your public posts and things you share on a mutual friend's Timeline. How to stop Facebook from revealing everything about you Review tags One of Facebook’s handiest privacy features is the ability to review posts you’re tagged in before they appear on your Timeline. They’ll still be visible on the News Feed while they’re fresh, but won’t be tied to your profile forever. In Timeline and Tagging, enable Timeline review controls. How to stop Facebook from revealing everything about you Clean up your apps You can view a list of all of the apps you’ve connected to your Facebook account by going to Settings and Apps. The list might be longer than you expected it to be. It’s worth tidying this up to ensure things you no longer use lose access to your personal information. If you don’t want to log into websites and apps with your facebook account, scroll down and turn Platform off. How to stop Facebook from revealing everything about you Change your ad preferences You can view a list of everything Facebook thinks you’re into and tinker with your ad preferences by going to Settings and Adverts. A lot more information is displayed on the desktop site than the app, so we’d recommend doing this on a computer. How to stop Facebook from revealing everything about you Download your data Facebook lets you download all of the data it has on you, including the posts you’ve shared, your messages and photos, ads you’ve clicked on and even the IP addresses that are logged when you log in or out of the site. It’s a hell of a lot of information, which you should download to ensure you never over-share on the social network again.

“There are people in Russia whose job it is to try to exploit our systems and other internet systems and other systems as well. We need to invest in getting better at this too,” he said.

“This is an arms race. They’re going to keep on getting better at this. And we need to invest in keeping on getting better at this too.”

Mr Zuckerberg, who said he did not believe his platform was a monopoly, claimed Facebook was going through “a broader philosophical shift in how we approach our responsibility as a company”. He said the company needs to take a “more proactive role” that included ensuring the tools it creates are used in “good and healthy” ways.

Going into the hearing, experts had said Mr Zuckerberg’s priority was to ensure it controlled as much as possible any regulation of companies such as this that politicians may seek to bring.

As it was, the politicians made his job easy, with several of them asking if he would work with them on the regulation. Asked by Senator Lindsey Graham if he supported regulation, Mr Zuckeberg replied: “If they are the right regulations, yes.”