WERE you one of more than 300,000 Australians caught up in Facebook's historic data breach?

There is as little-known way you can find out instantly in a Facebook tool that went live before the social network started rolling out warnings to more than 2 billion active users overnight.

The tool, which you can access here, will inform Facebook users whether they or one of their friends accessed the app created by Dr Aleksandr Kogan that harvested information from as many as 87 million people.

Click here to check if your data was harvested

Those whose information remained safe will receive a message stating, "based on our available records, neither you nor your friends logged into 'This Is Your Digital Life'.

As a result, it doesn't appear your Facebook information was shared with Cambridge Analytica by 'This Is Your Digital Life'."

Facebook will roll out warnings to users to tell them whether their personal information has been stripped and sold to a third party.
Facebook will roll out warnings to users to tell them whether their personal information has been stripped and sold to a third party.

Facebook is also due to roll out three types of warnings to users that will appear on their Newsfeeds overnight, which will indicate whether their information was exploited.

One will encourage users to change their settings, a second will warn that they used the suspect app and their information was scraped, while a third will inform the user their data was taken thanks to a friends' use of the app.

This message also confirms what details Cambridge Analytica took from users for the first time, adding "in most cases, the information (harvested) was limited to public profile, page likes, birthday, and current city".

All three messages do not apologise to users but say Facebook understands "the importance of keeping your data safe".

Facebook estimated 311,127 of its Australian users had personal information stripped from their profiles, sold to political data firm Cambridge Analytica, and used to influence elections.

Cambridge Analytica is currently under investigation by British authorities, before facing an audit by Facebook.

The social network faces investigations in several countries, including an official inquiry from the Australian Information Commissioner, and its founder Mark Zuckerberg will tomorrow face questions in a US Congressional committee.