Two German researchers say they have exposed the porn-browsing habits of a judge, a cyber-crime investigation and the drug preferences of a politician.
The pair obtained huge amounts of information about the browsing habits of three million German citizens from companies that gather “clickstreams”.
These are detailed records of everywhere that people go online.
The researchers argue such data – which some firms scoop up and use to target ads – should be protected.
The data is supposed to be anonymised, but analysis showed it could easily be tied to individuals.