Smartphone factory resets may not erase all personal data

Performing a factory reset on a smartphone does not always guarantee the permanent deletion of personal information. In many cases, deleting a file merely removes the pointer to that data and marks the space as available, leaving the actual content intact until it is overwritten by new information.

Research has demonstrated this vulnerability. A study by Avast involving 20 used Android devices that had undergone factory resets resulted in the recovery of thousands of photos, emails, text messages, and Google search histories. Similarly, researchers from the University of Cambridge found that on older Android versions, it was possible to recover previous owners' Google account access codes.

Modern smartphones have addressed this issue through standard encryption. Data is scrambled with a unique key known only to the device. When a factory reset is performed on current models, this encryption key is discarded, rendering any residual data unreadable even if it is recovered.