The good news: Facebook downgrades the number of accounts hit in the breach they disclosed two weeks ago to 29 million, down from 50 million. The bad news: Uh, that's still a LOT. And if you were one of those 29 million Facebook users, A LOT of your intimate personal data was stolen.
Facebook disclosed this in a corporate blog post, “An Update on the Security Issue,” with more details on the massive privacy breach.
Facebook Product Management VP Guy Rosen says:
People can check whether they were affected by visiting our Help Center. In the coming days, we’ll send customized messages to the 30 million people affected to explain what information the attackers might have accessed, as well as steps they can take to help protect themselves, including from suspicious emails, text messages, or calls.
This attack did not include Messenger, Messenger Kids, Instagram, WhatsApp, Oculus, Workplace, Pages, payments, third-party apps, or advertising or developer accounts.
Naturally they published at the end of the day on Friday, when all bad news gets dumped to minimize impact.
“For 15 million people, attackers accessed two sets of information — name and contact details (phone number, email, or both, depending on what people had on their profiles),” writes Rosen in the post.
“For 14 million people, the attackers accessed the same two sets of information, as well as other details people had on their profiles.”
Bu “other details,” he means your location, gender, relationship status, your recent search and personal physical location data.
Whoever carried out the attack also gained control of an additional million people's accounts, but didn’t access any of their data, Rosen writes.
As we’ve said, the attackers exploited a vulnerability in Facebook’s code that existed between July 2017 and September 2018. The vulnerability was the result of a complex interaction of three distinct software bugs and it impacted “View As,” a feature that lets people see what their own profile looks like to someone else. It allowed attackers to steal Facebook access tokens, which they could then use to take over people’s accounts. Access tokens are the equivalent of digital keys that keep people logged in to Facebook so they don’t need to re-enter their password every time they use the app.
Here’s how we found the attack that exploited this vulnerability. We saw an unusual spike of activity that began on September 14, 2018, and we started an investigation. On September 25, we determined this was actually an attack and identified the vulnerability. Within two days, we closed the vulnerability, stopped the attack, and secured people’s accounts by resetting the access tokens for people who were potentially exposed. As a precaution, we also turned off “View As.” We’re cooperating with the FBI, which is actively investigating and asked us not to discuss who may be behind this attack.
We now know that fewer people were impacted than we originally thought. Of the 50 million people whose access tokens we believed were affected, about 30 million actually had their tokens stolen. Here’s how it happened:
First, the attackers already controlled a set of accounts, which were connected to Facebook friends. They used an automated technique to move from account to account so they could steal the access tokens of those friends, and for friends of those friends, and so on, totaling about 400,000 people. In the process, however, this technique automatically loaded those accounts’ Facebook profiles, mirroring what these 400,000 people would have seen when looking at their own profiles. That includes posts on their timelines, their lists of friends, Groups they are members of, and the names of recent Messenger conversations. Message content was not available to the attackers, with one exception. If a person in this group was a Page admin whose Page had received a message from someone on Facebook, the content of that message was available to the attackers.
The attackers used a portion of these 400,000 people’s lists of friends to steal access tokens for about 30 million people. For 15 million people, attackers accessed two sets of information – name and contact details (phone number, email, or both, depending on what people had on their profiles). For 14 million people, the attackers accessed the same two sets of information, as well as other details people had on their profiles. This included username, gender, locale/language, relationship status, religion, hometown, self-reported current city, birthdate, device types used to access Facebook, education, work, the last 10 places they checked into or were tagged in, website, people or Pages they follow, and the 15 most recent searches. For 1 million people, the attackers did not access any information.
Facebook is working with the FBI, the FTC, and regulators in Ireland, and will continue to, Rosen wrote.
Here's the transcript for today's press call with Guy Rosen.