Although only 270,000 people are believed to have used the app, Cambridge Analytica was able to collect such a huge amount of data because, at the time, Facebook allowed developers to ask permission to collect data about users' friends. That means if someone you're friends with on Facebook signed in and used the This is Your Digital Life app, your data could have been shared with Cambridge Analytica without your knowledge. The firm has said it collected the data of 30 million users — or almost 100 times the number of people that actually, perhaps inadvertently, gave their consent — while Facebook says that number is potentially as high as 87 million.

The new support page also checks if any of your friends used the app. Facebook made a change in 2015 that greatly limited the data firms could collect from apps like this, including removing the ability for users to give permission for collection of their friends' data.

When The New York Times initially reported on the scandal, Facebook claimed that Cambridge Analytica's collection of data was within its policies and was what users had signed up for. However, it said the feeding of the data into a separate system for the purposes of advertising was against is terms of service and a "misuse" of the data.

The social network, and its CEO Mark Zuckerberg, has more recently admitted to not doing enough to prevent data misuse, and has committed to clearer privacy policies and more tightly controlled data sharing.