Australia's privacy watchdog is investigating Facebook over fears as many as one in 50 local users may have had their personal information accessed by Cambridge Analytica.
The Mark Zuckerberg-led multi-billion dollar social media giant has admitted 311,127 Australians are among the 87 million users worldwide whose data was unknowingly and "improperly" shared with the British political consulting agency.
The Privacy Commissioner will consider whether Facebook breached the Privacy Act, which requires organisations meet certain obligations including taking reasonable steps to ensure personal information is held securely.
Cambridge Analytica developed controversial tools for use in political campaigns and worked on Donald Trump's 2016 run for US president.
Facebook says the 87 million figure is their "best estimate" of the maximum number of accounts that installed CA's app, and the friends of those app users whose data may have also been shared.
Belinda Barnet, a data analytics expert at Swinburne University, says profile data like that collected by the group is just the tip of the iceberg.
Social media companies collect data on every click made on their websites and consider that information their property, leaving users unable to adjust access to it in privacy settings.
"All the data collected while you interact with the platform should be transparent, that should be available to you," Dr Barnet said.