How to find out if your Facebook data was accessed by Cambridge Analytica

Later today, April 9, Facebook will begin telling all of its 2.2 billion users whether their data was wrongfully accessed by Cambridge Analytica (CA).

A message will appear at the top of users' news feeds. The 87 million users whose data was taken by CA will receive a message explaining how their data fell into the hands of the British analytics company, while everyone else will receive a shorter message with a link to where on Facebook they can adjust their privacy settings, and see which companies have been granted access to their data.

Read More:

• Facebook reached into users' inboxes to delete messages sent to them by Mark Zuckerberg
• It's time to think seriously about your Facebook privacy settings
• This is what happens when you download everything Facebook knows about you
• Facebook damage limitation continues as privacy settings are simplified
• Zuckerberg insists he must remain at helm of Facebook despite data privacy scandal

The messages are due to appear from around 7am ET (4am PT), and arrive a day before Facebook boss Mark Zuckerberg is due to testify to Congress on April 10 and 11.

A whistleblower from CA first revealed that 50 million Facebook users had had their data wrongfully accessed, but Facebook itself then admitted the number was "up to" 87 million, with the majority being users in the US. Data was also taken from around a million users each in the UK, the Philippines and Indonesia.

For users in the clear, the message - which appears at the top of the Facebook smartphone app when they next open it, above the Stories section - reads: "[Name], we understand the importance of keeping your data safe, and are making it easier for you to control which apps you share information with.

"You can go to the Apps and Websites section of your settings anytime to see the apps and websites you've used Facebook to log into. You can also remove the ones you don't want connected to Facebook anymore."

The affected 87 million users will also receive this information, but Facebook also says: "We have banned the website 'This Is Your Digital Life', which one of your friends used Facebook to log into. We did this because the website may have misused some of your Facebook information by sharing it with a company called Cambridge Analytica...There is more work to do, but we are committed to confronting abuse and to putting you in control of your privacy."

If you receive the first message, that you are in the clear, then you should still take action. The link at the end of the message will take you to a page where you can manage which apps and websites have access to your data. We did this recently and found a long list of companies and services which had access to our details; some were expected and acceptable (Airbnb, for example), but others were apps or services we had used once years ago and since forgotten about.

If you have been on Facebook for years, as many users have, then there could be hundreds of apps, sites and services with access to your data. It is strongly recommended that you work through this list and remove any you are unfamiliar with, or no longer trust. Some may even have changed their names since you gave them permission to see your Facebook data, so it pays to be vigilant while doing this.