The myth of the phone without a SIM
Many people believe that removing the SIM card makes their phone invisible to companies and governments. That is a dangerous misconception. A phone without a SIM is still connected through Wi-Fi and Bluetooth, and it can send its unique IMEI to every network it detects.
Persistent identifiers: IMEI and MAC address
Your phone has several permanent hardware identifiers. The IMEI (International Mobile Equipment Identity) is a unique 15-digit number built into your device. The MAC address of your Wi-Fi chip is also a unique identifier. These numbers do not change when you remove your SIM, and they can be used to identify and track you.
Leaks through Wi-Fi
Even with no active connection, your phone constantly sends Wi-Fi "probe requests" to look for known networks. These signals contain your MAC address and reveal the networks you have connected to before, building a history of your movements and habits. Wi-Fi data collectors can map your movements without you knowing.
Apps that run in the background
Many apps keep collecting data even when offline and send it as soon as you reconnect to Wi-Fi. Messaging apps, social networks and even some system apps keep recording your activity, your contacts and your usage habits with no active SIM.
How to really protect your mobile privacy
For maximum protection, use airplane mode and turn Wi-Fi and Bluetooth off by hand. Consider alternative operating systems such as GrapheneOS or CalyxOS, which protect your privacy better. Use verified open-source apps and avoid those that ask for excessive permissions.
A phone without a SIM is not a silent phone. It keeps talking, just in a different voice.