Context

In recent weeks, you may have received a communication from the security team regarding the activation of a security measure requiring the use of your personal smartphone.

If you have not received it yet, you may receive it soon. In that case, make sure to verify the legitimacy of the request.

You can refuse

The communication may give the impression that this measure is mandatory, or even urgent.
What it does not specify is that you have the right to refuse to use your personal smartphone for professional purposes.