Barack Obama, facing the imminent handover to his bombastic successor, has plenty to be concerned about this week. But he took the time to express his concern about the impact of fake news online when he spoke to reporters on Thursday.

Obama, who was described in a detailed New Yorker interview as being “obsessed” with the problem since the election, described the new ecosystem of news online in which “everything is true and nothing is true”.

“In an age where there’s so much active misinformation, and it’s packaged very well, and it looks the same when you see it on a Facebook page or you turn on your television, where some overzealousness on the part of a US official is equated with constant and severe repression elsewhere, if everything seems to be the same and no distinctions are made, then we won’t know what to protect,” he told reporters in Berlin on Thursday. “If we can’t discriminate between serious arguments and propaganda, then we have problems.”



Obama is not exaggerating. Worse yet, in the last weeks of the US election campaign, according to an analysis by Buzzfeed News, fake news – whether claiming that the Pope had endorsed Trump, or that Clinton sold weapons to Isis – actually outperformed real news on the platform, with more shares, reactions and comments.



Another widely shared story used a young picture of Donald Trump with variations on a quote he reportedly gave People magazine in 1998. “If I were to run, I’d run as a Republican. They’re the dumbest group of voters in the country. They believe anything on Fox News. I could lie and they’d still eat it up. I bet my numbers would be terrific.”

Yet Trump never said that. It is not even possible to know how widely the quote was shared, with a new version created every time another is flagged, and removed. Memes like this replicate across the internet like a virus in this way, so the quote, tantalising in its plausibility, is pitch-perfect for quick sharing.

As long as Mark Zuckerberg refuses to understand his own system, there is no hope for Facebook reforming itself Siva Vaidhyanathan, University of Virginia

Facebook has faced many controversies in its 12 short years, but has fumbled with the gravity and impact of its editorial power in an age where 62% of US adults now turn to social media for some or all of their news, according to the Pew Research Centre.

In the early days of the election, Facebook was criticised for what was perceived as overzealous curation of its “trending topics” chart. When conservative outlets accused the site of censoring right-leaning news stories, Zuckerberg fired the trending stories team and replaced them with an algorithm – which almost immediately began to distribute fake news.



The problem went unaddressed. Sources told Gizmodo that high-level meetings in Facebook have been underway since May, when a planned update to identify fake news to Facebook’s news feed was shelved after it was found to disproportionately impact right-wing sites, though Facebook officially denies this happened.



Part of the problem, experts say, is that many people share articles based on the headline alone and don’t even read the story – let alone apply any skepticism to the claims within.



Another viral story by “the Denver Guardian” claimed, completely falsely, that an FBI agent investigating Clinton had been killed in a house fire in Colorado. It prompted the Denver Post – a newspaper that does actually exist and was founded in 1892 – to explain that “There is no such thing as the Denver Guardian”, pointing out that address it listed as its base led to a tree in a Denver carpark.



In one way, the problem is not a new one. Publications like the National Enquirer in the US have long bent the truth, often shamelessly. But now, a fake story can much more easily masquerade as real because in Facebook’s walled garden, all the posts look largely the same – a New York Times investigation alongside a fake story claiming Taylor Swift endorsed Trump.

The ease of deception has given birth to a brand new cottage industry. In November Buzzfeed discovered that many of the pro-Trump fake news sites – over 100 of them – were being operated as for-profit click-farms by Macedonian teenagers.

By 5 November, Facebook’s CEO Mark Zuckerberg was facing mounting pressure to address the problem. “Of all the content on Facebook, more than 99% of what people see is authentic. Only a very small amount is fake news and hoaxes,” he wrote on his Facebook page. “The hoaxes that do exist are not limited to one partisan view, or even to politics. Overall, this makes it extremely unlikely hoaxes changed the outcome of this election in one direction or the other.”



Experts say this statement sounds like Zuckerberg is in denial. “As long as Mark Zuckerberg refuses to understand his own system, there is no hope for Facebook reforming itself,” said Siva Vaidhyanathan, professor of media studies at the University of Virginia.

“Facebook and its leaders have consistently applauded themselves for connecting millions of people around the world and enabling friction-free conversation, and have gladly taken unwarranted credit for pro-democracy movements in different parts of the world,” he said. “And yet Zuckerberg himself has denied any moral responsibility for the fact that Facebook has helped poison American democracy.”

Facebook has faced criticism in the wake of the presidential election for its role in the distribution of fake news stories. Photograph: Lluis Gene/AFP/Getty Images

This weekend Zuckerberg openly acknowledged for the first time the gravity of the problem and the steps Facebook is taking to counter it.

“We take misinformation seriously,” he wrote in a post on Saturday. “We know people want accurate information. We’ve been working on this problem for a long time and we take this responsibility seriously.”

Zuckerberg said they were working to make it easier for users to report a story as fake. He also said Facebook has “reached out” to “respected fact-checking organizations” about third-party verification, but didn’t provide specifics.

The problem isn’t just limited to the latest US presidential election cycle, Vaidyanathan said. “The harmful information that spreads on Facebook includes the myths and lies about vaccination and links to autism. It contains myths and lies about the scientific fact of global warming. These are issues that are crucial to our wellbeing, and there is no algorithm that can distinguish a fact from a lie.”

On Monday, Google and Facebook both announced that they would be making it harder for fake news sites to make money via their advertising networks – though this does not address Facebook’s news feed problem.



Pressure continues to grow, even from within Facebook itself. A report emerged on Monday that a “renegade” group of “more than dozens” of Facebook employees had formed a task force, kept secret from upper management, to try to address the issue. “[Zuckerberg] knows, and those of us at the company know, that fake news ran wild on our platform during the entire campaign season,” an employee, speaking anonymously, told BuzzFeed. Hundreds more had privately expressed dissatisfaction with how the company had dealt with the problem.



Melissa Zimdars, assistant professor of communication and media at Merrimack College in Massachusetts, said she was concerned about some of the sources her students were finding and using online, so she created a Google document which lists a number of sites and which has since gone viral.



Not all of them are fake. Many are satirical sites such as the Onion or the New Yorker’s Borowitz Report, while others are news organizations whose stories are often slanted, like Breitbart on the right or Occupy Democrats on the left.



“There are things that readers can do, but there are [also] things structurally and within the culture of journalism itself that need to change,” Zimdars said. “One thing readers can do is to read what they’re sharing, and after that if you read something and have a strong reaction to it, read more about it rather than just accept what you originally read as complete information.”

The only solution to Facebook’s problem, according to Vaidhyanathan, is the labour-intensive human checking of facts.

“Facebook would have to hire thousands of human beings who are trained to make editorial judgments and could step in and edit news feeds,” he said. In the meantime, it’s as if Mark Zuckerberg is using some different version of Facebook unafflicted by hoax stories and misinformation. “The rest of us know too well the corrosive power of fake news.”