Google secretly tracked user browsing habits and passed the data on to advertisers, according to new reports.
An investigation by privacy-focused browser Brave found the search giant set up secret web pages to harvest user data that helped create profiles for targeted adverts.
The practice was uncovered by Brave's chief policy officer Johnny Ryan, who found his data was being traded on Authorized Buyers, Google‘s advertising exchange formally known as DoubleClick.
Ryan says that Google had labelled him with an identifying tracker that it fed to third-party companies that logged on to a hidden web page.
Brave then commissioned research with "hundreds of people" recruited to try and reproduce Ryan's experience, with the company finding that Google's practices did appear to create a secret web page identifier that was unique to each user. These identifiers were found to have been shared with multiple advertising companies in an attempt to boost the effectiveness of targeted advertising.
The evidence is now being reviewed by the Irish data regulator, with a potential GDPR fine on the way if Google is found to have broken data protection laws.
Google told the Financial Times that it was co-operating with the investigation, adding that, "we do not serve personalised ads or send bid requests to bidders without user consent."