I have a #Pixel 10 Pro XL phone, which may be the first phone to give warnings when the phone connects to a rogue cellphone tower or IMSI catcher. The OS cannot block it; it can only tell you that someone read information, and it presents an alert. It says,
"Your data may be at risk. Device ID accessed. At 6:57 PM a nearby network recorded your device's unique ID (IMSI or IMEI) while using your T-Mobile SIM. This means that your location, activity, or identity has been logged."
I didn't ever get an alert before walking through the building, but this time, during a 30-minute walk through the building, I got about 8 alerts, ranging between 1 and 3 minutes apart.
Using this information from repeated connections, someone can follow my movements and location; they can identify it's me because the IMSI number is unique to my phone, so it can be an indication that someone was collecting all the cellphone information in the area, most likely law enforcement.
It can also mean that I was connecting to a rogue cell phone tower, not just an IMSI catcher, and it was an attempted Stingray attack, likely also law enforcement. If successful, they can try to see and hear what I'm doing on my phone, as my phone won't know that it's a fake cellphone tower.
Be aware that a rogue tower will try to negotiate your phone's connection down to a 2G connection, which is unencrypted, providing them with access to everything that you are doing and saying. Please go into your phone's settings and disable 2G!!
It's been believed for some time that this technology has been used by law enforcement secretly and consistently. This is creepy and unnerving.
Turning off the phone, by the way, doesn't stop an IMSI catcher. Your phone still responds. You need to keep the phone in a Faraday bag if you're really concerned.
It's a good thing that phones are now starting to inform people that they are being watched and that people will begin to see how much of an issue this is. You can assume that your local law enforcement knows where you are all the time.