Users Data Recoverable, Android Factory Reset Setting 'Flawed'

Are you planning to junk your smartphone in the second-hand device market for the sake of a new one?

Some half a billion Android mobile devices from leading brands such as Samsung and HTC have a flawed "factory reset" function which leaves sensitive information including passwords, contacts, emails, media files and text messages recoverable after a device is "wiped".

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Even when full-disk encryption is in place, sensitive data is still recoverable because the factory reset process on affected models fails to erase the files which store decryption keys, a Cambridge University study has shown.

The study examined 21 second-hand devices running Android versions from five manufacturers that had been wiped using the operating system's built-in factory reset feature.

But the problems also exist with third-party data deletion applications, such as those offered by antivirus vendors, the researchers said.

The team was able to recover data including multimedia files and login credentials from wiped phones, and many of the handsets yielded the master token used to access Google account data, such as Gmail and Google Calendar.

The problem results from multiple issues, including the inherent difficulty of fully deleting data from the flash memory used in smartphones, something due to the physical nature of such memory chips, according to the research.

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Other issues include vendors' failure to include necessary drivers or failures introduced by their modifications of Android for individual devices.

Devices protected with encryption can still be accessed, because the file storing the decryption key is not erased, making it accessible to cracking, the study said.