Facebook hearings: Fact-checking some of Mark Zuckerberg's most strange claims to US politicians

It was almost painful to watch Zuckerberg trying to explain the Cambridge Analytica scandal to a bunch of older non-digital natives (Getty)

Mark Zuckerberg made his way through a huge grilling from US politicians mostly unscathed. But attention is now turning to some of the more chilling and confusing claims he made during the questioning.

Much of the time was taken up with the Facebook boss apologising and promising to do better. But Mr Zuckerberg also suggested that Facebook is not tracking people around the internet, and that if they wanted to they could simply turn off the collection of data for advertising purposes.

Neither of those things is strictly true, and Facebook itself admits as much on its website. It is not clear if Mr Zuckerberg was unaware of the full scale of his own site's tracking of its users.

Perhaps most chilling, and a little confusing, was a point that Mr Zuckerberg was asked to return to on the tracking of people's browsing history. He claimed that was done – but later, after talking with his team, admitted that it does actually track people's browsing history for ad purposes.

Still, he said that data is only taken temporarily and used to work out people's interests, when it is deleted. That is why browsing data will not show up when people request all the data has on them, he claimed.

1. 'Facebook only tracks people around the internet for security purposes'

   ZUCKERBERG: "There may be specific things about how you use Facebook, even if you're not logged in, that we — that we keep track of, to make sure that people aren't abusing the systems."

   At a different point in the hearing, he said: "In general, we collect data of people who have not signed up for Facebook for security purposes."

   THE FACTS: Facebook collects data on your online habits wherever it can find you, and very little of it appears to be for security purposes.

   Facebook pays third-party websites and apps to let it place tracking code across the internet and mobile devices. That code can be embedded in browser files called "cookies," invisible screen pixels, or Facebook's familiar "like" and "share" buttons.

   That code then reports back to Facebook on your surfing habits to help it better target ads. Along with Google, Facebook is consistently among the top three data-collectors in the field, said Reuben Binns, an Oxford University computer scientist who researches these beacons.

   In February, a Belgian court ruled that Facebook had violated European privacy law with such tracking because it hadn't obtained consent either to collect or store the data.

2. 'Users can just switch off advertising data'

   ZUCKERBERG: "There is a setting so if you don't want any data to be collected around advertising, you can turn that off and then we won't do it."

   THE FACTS: There is no such single setting on Facebook.

   You can limit ad targeting, but it requires several steps, which you may have to repeat from time to time. By default, Facebook shows you ads based on interests you've expressed over the years and the companies you have "interacted" with — for instance, by sharing your email or phone number, visiting their website or using their app.

   You can turn off such targeted ads with a single option in your Facebook settings. Doing so means, for example, that you won't get an ad on Facebook for a pair of shoes you just looked at on a shopping website, though you'll still get generic ads.

   But that doesn't stop the data collection. Facebook also adds targeting categories based on your demographic information, such as whether you might have a child, your birthday and age, what mobile device you use and even your political leanings — whether or not you've explicitly shared any of that on Facebook.

   Turning off those categories is a chore, as you have to select them one by one in settings. And if you like a new page, click on a new ad or add your email to a new business's contact list, the whole thing starts over.

3. 'People can take all the data Facebook has and use it elsewhere'

   ZUCKERBERG: "People have the ability to see everything they have in Facebook, take that out, delete that account and move their data anywhere that they want."

   THE FACTS: That's only partly true.

   You can indeed download a subset of the information it has collected on you. But the resulting file mostly contains a jumble of contacts, messages and advertisers who have been allowed to target you through Facebook.

   That makes the information mostly useless if you hoped to use it to join a different social network, because it's incomplete and not organized in a way that another service could easily import.

   Experts say Facebook has made it technically untenable to take your data elsewhere. University researchers have tried to figure out how to make that data portable, but failed because Facebook keeps changing the public-facing software required.

   There are other issues that make true data portability vexing. Zuckerberg alluded to one on Wednesday: Who owns material shared across a social network to multiple users? "Let's say I take a photo and I share it with you. Now is that my photo or is it your photo?" he said.

   Additional reporting by AP