Deactivate your sim card when traveling with a group

You should not use the SIM card to make calls, send text messages or use your mobile internet connection. To be on the safe side, remove it from your phone or activate flight mode.

If you move through identical radio cells with other people over a longer period of time, it is theoretically possible to narrow down who you could be or who your family or friends are. This also applies if you use an anonymous SIM card. The shared cell changes may be logged in your provider's traffic data. If these are merged, it may be possible to determine who you were traveling with. Ask friends to provide you with a Wi-Fi hotspot if you are traveling and need Internet access. Use this with a VPN or Tor for security. If you are traveling with a larger group, only one person should create a hotspot. Everyone else should remove their SIM cards for this time or activate flight mode.