Most Australians already didn't trust Facebook to keep their data safe even before the Cambridge Analytica scandal broke.

A YouGov Galaxy poll, commissioned by News Corp Australia before it was revealed the data mining company had tapped the data of 50 million FB users, showed 62 per cent didn't trust the social media behemoth.

"If the survey was re-run now ... the level of trust in Facebook would have slumped significantly -- and it was starting from a low benchmark," YouGov Galaxy managing director David Briggs told News Corp on Saturday.

About 84 per cent want to be able to opt out of having their information held by FB while 80 per cent feared identify theft, according to the survey.