Pedro Canahuati, VP Engineering, Security and Privacy

As part of a routine security review in January, we found that some user passwords were being stored in a readable format within our internal data storage systems. This caught our attention because our login systems are designed to mask passwords using techniques that make them unreadable. We have fixed these issues and as a precaution we will be notifying everyone whose passwords we have found were stored in this way.

To be clear, these passwords were never visible to anyone outside of Facebook and we have found no evidence to date that anyone internally abused or improperly accessed them. We estimate that we will notify hundreds of millions of Facebook Lite users, tens of millions of other Facebook users, and tens of thousands of Instagram users. Facebook Lite is a version of Facebook predominantly used by people in regions with lower connectivity. (Update on April 18, 2019 at 7AM PT: Since this post was published, we discovered additional logs of Instagram passwords being stored in a readable format. We now estimate that this issue impacted millions of Instagram users. We will be notifying these users as we did the others. Our investigation has determined that these stored passwords were not internally abused or improperly accessed).

In the course of our review, we have been looking at the ways we store certain other categories of information — like access tokens — and have fixed problems as we’ve discovered them. There is nothing more important to us than protecting people’s information, and we will continue making improvements as part of our ongoing security efforts at Facebook.

How We Protect People’s Passwords

In line with security best practices, Facebook masks people’s passwords when they create an account so that no one at the company can see them. In security terms, we “hash” and “salt” the passwords, including using a function called “scrypt” as well as a cryptographic key that lets us irreversibly replace your actual password with a random set of characters. With this technique, we can validate that a person is logging in with the correct password without actually having to store the password in plain text.

Because we know that people may share, reuse or have their passwords stolen, we’ve built security measures to help protect people’s accounts:

• We use a variety of signals to detect suspicious activity. For example, even if a password is entered correctly, we will treat it differently if we detect that it is being entered from an unrecognized device or from an unusual location. When we see a suspicious login attempt, we’ll ask an additional verification question to prove that the person is the real account owner.
• People can also sign up to receive alerts about unrecognized logins.
• Knowing some people reuse passwords across different services, we keep a close eye on data breach announcements from other organizations and publicly posted databases of stolen credentials. We check if stolen email and password combinations match the same credentials being used on Facebook. If we find a match, we’ll notify you next time you login and guide you through changing your password.
• To minimize the reliance on passwords, we introduced the ability to register a physical security key to your account, so the next time you log in you’ll simply tap a small hardware device that goes in the USB drive of your computer. This measure is particularly critical for high-risk users including journalists, activists, political campaigns and public figures.

Securing Your Account

While no passwords were exposed externally and we didn’t find any evidence of abuse to date, here are some steps you can take to keep your account secure:

• You can change your password in your settings on Facebook and Instagram. Avoid reusing passwords across different services.
• Pick strong and complex passwords for all your accounts. Password manager apps can help.
• Consider enabling a security key or two-factor authentication to protect your Facebook account using codes from a third party authentication app. When you log in with your password, we will ask for a security code or to tap your security key to verify that it is you.

For more information on how to keep your Facebook account secure, please visit facebook.com/about/security.