Facebook, WhatsApp and Instagram Go Down in Major, Worldwide Outage

"They don't know how to contact the people in their lives without it," she said. "They're more susceptible to social engineering because they're so desperate to communicate." Tobac said that during previous outages, some people received emails promising to restore their social media account if they would click on a malicious link that would expose their personal data.

The cause of the outage remains unclear. Madory said it appears that Facebook withdrew "authoritative DNS routes" that let the rest of the internet communicate with its properties.

Such routes are part of the internet's domain name system, or DNS, a key structure that determines where web traffic needs to go. DNS translates an address like "facebook.com" to an IP address like 123.45.67.890. If Facebook's DNS records disappeared, apps and web addresses would be unable to locate it.

Jake Williams, chief technical officer of the cybersecurity firm BreachQuest, said that while foul play cannot be completely ruled out, chances are good that the outage is "an operational issue" caused by human error.

Madory said there was no sign that anyone but Facebook was responsible, and discounted the possibility that another major internet player, such as a telecom company, might have inadvertently rewritten major routing tables that affect Facebook. "No one else announced these routes," said Madory.

Twitter, meanwhile, chimed in from the company's main Twitter account, posting "hello literally everyone" as jokes and memes about the Facebook outage flooded the platform. Later, as an unverified screenshot suggesting that the facebook.com address was for sale circulated, Twitter CEO Jack Dorsey tweeted, "how much?"

The outage comes as Facebook faces a separate major crisis after whistleblower Frances Haugen, a former Facebook product manager, provided The Wall Street Journal with internal documents that exposed the company's awareness of harms caused by its products and decisions. Haugen went public on "60 Minutes" on Sunday and is scheduled to testify before a Senate subcommittee on Tuesday.

Haugen also had anonymously filed complaints with federal law enforcement alleging that Facebook's own research shows how it magnifies hate and misinformation and leads to increased polarization, and how Instagram, which it owns, specifically can harm teenage girls' mental health.

The Journal's stories, called "The Facebook Files," painted a picture of a company focused on growth and its own interests over the public good. Facebook has tried to play down the research. Nick Clegg, the company's vice president of policy and global affairs, wrote to Facebook employees in a memo Friday that "social media has had a big impact on society in recent years, and Facebook is often a place where much of this debate plays out."