The data they recovered includes contacts, images and videos, texts, emails and log-ins for third-party apps like Facebook and WhatsApp. They were also able to retrieve the master token needed to access all Google user data in 80 percent of the phones. There are many possible reasons for reset failure: according to the researchers, manufacturers sometimes don't load a phone's software with the drivers needed to completely wipe its internal disk or SD card add-on. Also, flash drives are notoriously difficult to erase.

It's unclear at the moment if Google or any of the manufacturers whose phones were tested are doing anything about this issue. But if you really want to protect your info before tossing, selling or giving away an old phone, use the most complicated password you can whip up... or, you know, go to town on it with a hammer.