It's quite possible, in the past six months or so, that you've been among the millions of people who have had personal data stolen by criminals, after three of the biggest hacks in Australia's history were publicly disclosed. 

Optus, Medibank and, this month, Latitude Financial have all fallen prey to malicious cyber-attacks, but they're just the ones we know about. 

So what don't we know about? 

Today, a data researcher on the thousands of breaches that are hidden from the public. 

Featured: 

Dr Jane Andrew, professor, University of Sydney Business School