“We were able to fix the vulnerability and secure the accounts, but it definitely is an issue that it happened in the first place.”
Mark Zuckerberg, Facebook
Facebook says that affected users will see a message at the top of their News Feed about the issue when they log back into the social network. “Your privacy and security are important to us,” the update reads. “We want to let you know about recent action we’ve taken to secure your account.” The message is followed by a prompt to click and learn more details. If you were not logged out but want to take extra security precautions, you can check this page to see the places where your account is currently logged in, and log them out.
Facebook has yet to identify the hackers, or where they may have originated. “We may never know,” Guy Rosen, Facebook’s vice president of product, said on a call with reporters Friday. The company is now working with the Federal Bureau of Investigation to identify the attackers. A Taiwanese hacker named Chang Chi-yuan had earlier this week promised to live-stream the deletion of Mark Zuckerberg’s Facebook account, but Rosen said Facebook was “not aware that that person was related to this attack.”
“If the attacker exploited custom and isolated vulnerabilities, and the attack was a highly targeted one, there simply might be no suitable trace or intelligence allowing investigators to connect the dots,” says Lukasz Olejnik, a security and privacy researcher and member of the W3C Technical Architecture Group.
On the same call, Facebook CEO Mark Zuckerberg reiterated previous statements he has made about security being an “arms race.”
“This is a really serious security issue, and we’re taking it really seriously,” he said. “I’m glad that we found this, and we were able to fix the vulnerability and secure the accounts, but it definitely is an issue that it happened in the first place.”
The social network says its investigation into the breach began on September 16, when it saw an unusual spike in users accessing Facebook. On September 25, the company’s engineering team discovered that hackers appear to have exploited a series of bugs related to a Facebook feature that lets people see what their own profile looks like to someone else. The “View As” feature is designed to allow users to experience how their privacy settings look to another person.
The first bug prompted Facebook’s video upload tool to mistakenly show up on the “View As” page. The second one caused the uploader to generate an access token—what allows you to remain logged into your Facebook account on a device, without having to sign in every time you visit—that had the same sign-in permissions as the Facebook mobile app. Finally, when the video uploader did appear in “View As” mode, it triggered an access code for whoever the hacker was searching for.
“This is a complex interaction of multiple bugs,” Rosen said, adding that the hackers likely required some level of sophistication.
That also explains Friday morning’s logouts; they served to reset the access tokens of both those directly affected and any additional accounts “that have been subject to a View As look-up” in the last year, Rosen said. Facebook has temporarily turned off “View As,” as it continues to investigate the issue.
“It’s easy to say that security testing should have caught this, but these types of security vulnerabilities can be extremely difficult to spot or catch since they rely on having to dynamically test the site itself as it’s running,” says David Kennedy, the CEO of the cybersecurity firm TrustedSec.
The vulnerability couldn’t have come at a worse time for Facebook, whose executives are still reeling from a series of scandals that unfolded in the wake of the 2016 US presidential election. A widespread Russian disinformation campaign leveraged the platform unnoticed, followed by revelations that third-party companies like Cambridge Analytica had collected user data without their knowledge.
“There simply might be no suitable trace or intelligence allowing investigators to connect the dots.”
Security Researcher, Lukasz Olejnik
The social network already faces multiple federal investigations into its privacy and data-sharing practices, including one probe by the Federal Trade Commission and another conducted by the Securities and Exchange Commission. Both have to do with its disclosures around Cambridge Analytica.
It also faces the specter of more aggressive regulation from Congress, on the heels of a series of occasionally contentious hearings about data privacy. After Facebook’s announcement Friday, Senator Mark Warner (D-Virginia), who serves as vice chairman of the Senate Intelligence Committee, called for a “full investigation” into the breach. “Today’s disclosure is a reminder about the dangers posed when a small number of companies like Facebook or the credit bureau Equifax are able to accumulate so much personal data about individual Americans without adequate security measures,” Warner said in a statement. “This is another sobering indicator that Congress needs to step up and take action to protect the privacy and security of social media users.”
Facebook may also face unprecedented scrutiny in Europe, where the new General Data Protection Regulation, or GDPR, requires companies to disclose a breach to a European agency within 72 hours of it occurring. In cases of high risk to users, the regulation also requires that they be notified directly. Facebook says it has notified the Irish Data Protection Commission about the issue.
This is the second security vulnerability that Facebook has disclosed in recent months. In June, the company announcedit had discovered a bug that made up to 14 million people’s posts publicly viewable to anyone for days. This is the first time in Facebook’s history, though, that users’ entire accounts may have been compromised by outside hackers. Its response to this vulnerability—and the speed and comprehensiveness of the important disclosures ahead—will likely be of serious importance. Once again, all eyes are on Mark Zuckerberg.
Additional reporting by Lily Hay Newman.