Biometric Data Security: Your Guide to Selling a Smartphone Safely

Learn how to securely delete biometric data before you sell your smartphone while protecting your privacy and preventing data leaks.

Aug 31, 2023 - 3 min.

Smartphones with biometric security features offer a decisive advantage. Users no longer have to remember long and cumbersome PIN codes – the device can be unlocked using a fingerprint or facial scan instead. Access to many applications (such as banking apps) is also a breeze, thanks to biometric authentication. This makes it easy for users to access their most sensitive data themselves. Smartphones have become consumer goods. European users replace their devices every 40 months on average. When the time comes to sell or recycle an old mobile phone, many wonder if their biometric data is still stored even after they reset their phone to factory settings. Read this blog post to learn how to ensure that all data on your smartphone is deleted before you sell it – and what risks you run if you don't do this properly.

Biometric data on mobile phones and the danger posed by cyber criminals

The term' biometrics’ is generally used to describe the statistical and mathematical measurement of individual physical or biological characteristics for identification purposes. In the field of cyber security, biometric identification refers to the use of unique biological characteristics for digital authentication and access control purposes.

In this context, biometric authentication methods are highly secure and offer numerous application possibilities. Biometric methods are increasingly being utilised – especially in cyber and data security. On the one hand, biometrics give users a quicker and more convenient way of logging in to accounts and other security processes while making them more difficult to manipulate without authorisation.

On the other hand, the wide-ranging uses of biometric data in public surveillance are leading to growing concerns regarding data protection and security. If biometric data is compromised, this also increases the risk of identity theft and fraudulent activities.

Especially on the darknet, it's no longer just passwords and user names being traded, but increasingly biometric data as well. This covers the entire spectrum, from identity cards to authentication data.

Despite this trend, many people are still extremely careless in treating their biometric data. Yet once data falls into the wrong hands, it’s practically lost forever. This is why you should delete all sensitive information – including biometric data – from a mobile phone before selling it. But even after you reset your smartphone, there are some things to consider.

Biometric data remains on the device despite a reset

Resetting a smartphone to factory settings does not automatically delete all personal data and settings. Some manufacturers implement security measures to prevent biometric data from being permanently deleted by mistake. 

Which data remains on the smartphone also depends on the type of security function the device uses. For instance, it’s common for fingerprint or facial recognition data to be stored in encrypted form. This makes it more difficult for cybercriminals to access the data. 

Deleting biometric data from a smartphone can be complex and depends on several factors – such as the operating system used, data encryption and residual data (remnants in the device’s memory areas). However, most modern operating systems, such as iOS and Android, usually offer the option to delete the biometric information stored on the device.

Tips for deleting biometric data

To protect your smartphone before selling or recycling it, you should follow these steps: 

  1. Data backup:
    Before you decide to reset, sell or recycle the smartphone, it’s important that you save all your important and personal data, such as photos and contacts, on another device or in the cloud.
  2. Deactivate the biometric function:
    Before resetting the device, disable all biometric functions such as fingerprint and facial recognition. This ensures that no sensitive information remains on your smartphone. 
  3. Completely reset the smartphone:
    To ensure that no data remains on the device, you should reset your mobile phone to factory settings. All data on the internal memory and SD cards should be removed. 
  4. Remove the SIM and SD card:
    These also contain sensitive data, so remove them before selling. 
  5. Follow the manufacturer’s instructions:
    To ensure that all your information is deleted from your smartphone, it’s important to read the instructions provided for the device. This is the only way to ensure that all manufacturer-specific instructions have been followed.
  6. Seek professional advice:
    Sometimes, it may be wise to use a professional service provider or software to ensure that the biometric data has been completely erased. 

Using biometric security features on smartphones undoubtedly offers convenience and increased security. But don’t be complacent by underestimating the importance of properly deleting your biometric data if you decide to sell or recycle your old smartphone. The temptation of relying on a simple factory reset is understandable but not always sufficient to remove sensitive biometric information effectively.


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