Your metadata can tell so much about you that those looking at it may not even need the content.
Security-conscious tech experts hope to broaden awareness about issues in digital privacy by inviting teams on Saturday to track down a journalist's source armed with only metadata and a desktop computer.
The 'snitch hunt', using mock data and identities, will show participants how much can be learnt about someone just from the phone and internet records that 22 government agencies can access without a warrant.
"This information provides a pretty detailed picture of the life we lead," University of Melbourne researcher Suelette Dreyfus told AAP on Friday.
"You can draw a set of conclusions about people who visit the psychiatrist, mental health clinics, sexual health clinics, marriage counsellors... you can gain a lot of information about someone's personal life by having access to their metadata."
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This will be tested at the free Snitch Hunt event at the University of Melbourne on Saturday that is open to people of all ages and technical abilities.
Teams that have already registered for the event include a group of 10-14-year-olds called the Clever Girls.
They all will act as data analysts and trawl through collections of data to see who has been tipping off the journalist to corporate wrongdoings.
Dr Dreyfus advises whistleblowers in the digital age stay well away from SMS.
"Using SMS is one of the worst things you can possibly do," she said.
"At the very least, use an encrypted chat program, like Signal or Wickr."
But be warned, the connection between journalist and source on secure messaging apps may still be discovered depending how each party uses the app and the investigation.
For anonymity, she suggests using the freely-available program, Tor, or snail mail.
The Snitch Hunt is organised through University of Melbourne and is co-sponsored by partners including ThoughtWorks, CryptoParty Sydney, Blueprint for Free Speech, Hack For Privacy, Platypus Initiative, Digital Rights Watch and Electronic Frontiers Australia.
