How far can Bluetooth be connected

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Only switch on when necessary?

No Bluetooth device can be attacked if it is switched off. Therefore, the most important advice of all experts is: only turn on Bluetooth when you want to connect.


Special case: Corona warning app

The Corona warning app only works if Bluetooth is permanently activated. It is important here to weigh the risks and the expected benefits against each other.

In fact, the risk of being attacked through a Bluetooth vulnerability is very small. Because the attacker must be in close proximity to the attacked device. This is of no interest to most of the cybercriminals' business models - they tend to attack as many devices as possible automatically at the same time.

This is also reflected in the reporting: there are relatively often weak points in the Bluetooth function. However, there are virtually no reports of actual attacks outside the laboratory. Should the app actually make a contribution to keeping the corona epidemic in check, that would be a tangible benefit.

However, the activated Bluetooth function remains a risk. We therefore particularly recommend using a device that is supplied with the latest security updates for this app.

Couple devices securely - this is how it works

Choose a strong PIN

When pairing two devices, you may be asked to enter a combination of numbers. To do this, choose at least eight digits and no standard sequences such as 12345678.


Only pair and connect known devices

Do not accept a pairing request if you are unsure who it is from. Do not accept a connection request from devices that are already paired if it comes as a surprise and you cannot understand who is using the requesting device.


Peripherals should indicate connection

When purchasing Bluetooth devices such as headsets, headphones, or speakers, choose devices that show existing connections. Usually a light then lights up. This allows you to notice when the device makes unexpected connections that were not initiated by you.


Devices should not always be ready to pair

Do not use devices that automatically go into “pairing mode” when you turn them on. Good headsets or headphones have to be switched to this mode at the push of a button in order to pair new devices. This means that nobody can pair and connect later unnoticed if they have unobserved access to the device.


Coupling with standard PIN

Bluetooth devices that use unchangeable standard PINs for coupling (e.g. 0000) require special attention. Find out whether the device can pair with several different partners. If so, a third party could, for example, pair their smartphone with your headset without your knowledge.

If the device is automatically ready to pair as soon as it is switched on, this can even happen without the attacker holding the device in their hands. Do not leave such devices turned on when you are not using them.


Beware of headsets

Do not leave Bluetooth headsets turned on. Especially not if they are used by different people. A third party could connect to the device unnoticed and eavesdrop on your conversation.


Tidy up connections and decouple devices

Check regularly which devices are paired with your mobile device. Connections that are no longer required should be removed. Once paired, devices can otherwise connect without authentication - even if they are no longer in your possession.

Switch off location via Bluetooth

Cell phones can also determine their own location via Bluetooth. The device searches for Bluetooth connections in the area, for example from beacons. Beacons are small Bluetooth transmitters that are installed in shop windows, for example. Then the mobile phone sends the unique ID of the respective Bluetooth transmitter to Google.

This does not stop when users have deactivated the Bluetooth function. If you want to let Bluetooth rest completely, you have to select it separately elsewhere.


Use the current standard

Do not use devices that use Bluetooth 2.1 or older. In these versions the encryption is not reliable and can be deactivated. The Bluetooth version can be found in the device information, in the smartphone in the properties of the Bluetooth app.

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