Live: Mark Zuckerberg testifies before US Congress

We're done. The congressional hearing has wrapped up after a mammoth five hours of questioning for Zuckerberg. He will return tomorrow to face the House.

Some observations from today:

• The 44 senators who asked questions today were obviously and unfortunately not well-versed in this topic. It was a classic example of Donald Rumsfeld's "unknown unknowns". As one commentator said: "His questioners have no idea just how clueless most of their enquiries were".
• Zuckerberg will be pleased with his performance. He was fairly well-spoken, unflappable and answered questions with contrition but without giving too much away.
• He apologised for Facebook's mishandling of users' data but strongly defended its core business model of making money from the personal information its customers post on their accounts.
• The rest of us come away with, well, not much. Facebook knows it has really messed up. Facebook promises they're doing a bunch of stuff to fix it. Users still have no idea if anything will really change.

A juicy little tidbit here that explains Senator Ted Cruz's somewhat bizarre question on the firing of Palmer Luckey.

Zuckerberg shared this Facebook post this morning on his way to Capitol Hill. I think he'll be fairly pleased with how he's gone during his testimony - he's followed the script, he hasn't been caught out by anything tricky, he has shown contrition and he has agreed to further, unspecified action around regulation.

Zuckerberg is asked if there have been any privacy breaches or 'hacks' aside from Cambridge Analytica.

​He says he doesn't believe there has been another breach of data. There was one hack in 2013 when someone was able to install malware on some employees' computers but he doesn't believe it affected users.

This Tweets neatly sum up today's marathon hearing (which is still going - eight senators left to ask questions).

The questions have been vague and overly broad (how can you protect people's data?) or weirdly specific (like questions on why certain pages have been removed or whether internet connectivity can be better in the state of West Virginia).

Each senator has lambasted Zuckerberg but actually doesn't really know what they want to regulate.

Zuckerberg has just promised Senator Maggie Hassan that Facebook will work with Congress towards a suitable framework of regulation.

However, he doesn't quite agree when Hassan suggests introducing financial penalties for breaches. He says Facebook already has a financial incentive to do things properly.

"This episode has clearly hurt us," he says. "And has cleary made it harder for us to achieve the social mission we care about. We now have to do a lot of work to build trust back."

Zuckerberg, once again, is defending the advertising model of Facebook and saying that he believes it is the right model.

If it weren't for this model, people would most likely have to pay for Facebook.

He said many users wouldn't be able to pay and it's against the ethos of the company.