The flaw in factory resets

Encryption. (

Encryption. (

Every phone and tablet has an option under Settings that allows you to Reset Phone to Factory Defaults. When activating this option the phone warns you that it will delete all your information, pictures, music, e-mail, apps and everything else that you have loaded on the device. Essentially the phone is reset to the point where it came out of the factory and ready to be setup for the first time.

But is this good enough? Is your information really deleted? The shocking answer is: No.

What happens when you delete ?

When we create a file, such as when we snap a new pic or create a new document, the operating system creates the file by storing it in bits and pieces in blocks on the device’s storage – be it internal phone storage or SD Card. 

In order to find which blocks make up the file, the operating system creates an index that identifies the bits that make up the complete file.

When you delete a file, the operating system removes not the content inside the blocks, but removes the reference to those blocks from the Index. However, all the bits in the blocks still remain on the hard drive and are marked as “free” so that new files can overwrite those bits. It’s the equivalent of removing the chapter name from the Index of the book, but still leaving the contents of the chapter inside the book – if you page through, you will find that chapter even without the index.

And this is where the problem arrises.

There are applications that allow techies to skip over the index and view the bits inside those blocks so they can recover any file whose blocks haven’t been overwritten by new files.

Does Factory Reset leaves content behind?


This is confirmed by the team at security firm Avast, who purchased 20 phones on eBay and ran their software though them that have been reset to Factory Defaults. They discovered over 40 000 photos (yes, including those sexting pics), 750 e-mails, 250 contacts with names and addresses and various personal files.

Stefan Tanase, Senior Security Researcher, Global Research & Analysis Team, Eastern Europe, Middle East and Africa, Kaspersky Lab confirms this too: “A staggering amount of personal data is usually left on devices after a factory reset is performed. Most often these devices end up being sold on eBay(-like) websites, and might end up in the hands of someone with bad intentions, who can recover the data. Users don’t realise that they leave behind e-mails or SMS messages, contact information or even personal pictures and videos shot with the phone camera. Essentially, all data stored on the device is recoverable to some extent.”

How do you do you ensure that your data is actually deleted ?

Simply doing a factory reset clearly is not the answer. If you want to ensure that none of your sensitive pics or information land up all over the Internet, you should Encrypt your device before doing Factory Reset. 

This sounds very “James-Bondy” but it s a simple step that you need to do with the tool included with your phone. When you run the encryption tool, it protects your files from prying eyes which goes a long way to stop anyone with $50 software from getting a hold of your  family pics.

Each phone manufacturer has their own way of dealing with encryption:

Obviously before engaging in this, make sure you read and understand what is involved and back up your phone (do not lose the PIN either.)


iOS 8 (already comes encrypted)

BlackBerry devices

If your device doesn’t have encryption built into the settings, then you can download several applications from the App Stores that allow you to do that.

The obvious solution would be for the mobile phone manufacturers to have encryption built into their Factory Reset process, however as Stefan Tanase  points out that the mobile phone manufacturers chose not to do this because of:

1. Lack of security awareness – both users and manufacturers generally don’t realise the importance of securely erasing data.

2. Speed – erasing a storage device securely takes more time, and the reality is that most users would rather have their device quickly perform the factory reset.

The more we trust our mobile phones with out lives, the more we should be weary of just how vulnerable these devices are. We need to be more aware of the digital fingerprints we are leaving behind.

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