If you're running Android you should probably check this
"Are you worried that someone may be intercepting your phone calls and SMSs? Well, you might not be just paranoid, and it’s not just about spying programs installed on your mobile device.
The privacy and information security community has been warning people for years about stingray attacks, a technique that consists of deploying a device that masquerades as a cell tower, forcing cell phones within range to connect to it. The attackers then intercept all data transmitted. There’s dozens of documented cases in which both law enforcement and private entities deployed stingray attacks to spy on protestors, dissidents or other persons of interest.
The bad news is all mobile phones are vulnerable to this type of attack, and there isn’t much you can do to prevent it. However, there’s also a silver lining. Most of these vulnerabilities have been addressed in 4G, which forces attackers to usually downgrade the connection to 2G, an old standard susceptible to flaws. Until recently, users couldn’t prevent their phones from switching to 2G but, with Android 12, Google has quietly rolled out the option to disable 2G on your Android device"
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