Google has admitted that for the past three years it has wrongly collected information people have sent over unencrypted wi-fi networks.
The issue came to light after German authorities asked to audit the data the company's Street View cars gathered as they took photos viewed on Google maps.
Google said during a review it found it had "been mistakenly collecting samples of payload data from open networks".
The admission will increase concerns about potential privacy breaches.
These snippets could include parts of an email, text or photograph or even the website someone may be viewing.