From EFF:

Apple has also finally taken steps to protect users against cell site simulators after being called on to do so by EFF and the broader privacy and security community. Apple announced that in iOS 17, out September 18, iPhones will not connect to insecure 2G mobile towers if they are placed in Lockdown Mode. As the name implies, Lockdown Mode is a setting originally released in iOS 16 that locks down several features for people who are concerned about being attacked by mercenary spyware or other nation state level attacks. This will be a huge step towards protecting iOS users from fake base station attacks, which have been used as a vector to install spyware such as Pegasus.