Apple mentioned in the iOS security white paper: "In order to prevent devices from being downgraded to a software version that lacks the latest security updates, iOS uses a process called system software authorization. If the downgrade is allowed, attackers who can physically access the device will be able to install the earlier version of iOS and take advantage of the fixed security vulnerabilities in the new version of iOS. "

Therefore, Apple has started the step of verifying the system, that is, if the system detects that the system version that needs to be downgraded is the version whose verification has been turned off, then it can't pass the server signature verification, so it can't be downgraded smoothly, so Apple devices can't go back to verifying the system version that has been turned off.

Extended data

IOS specially designed the underlying hardware and firmware functions to prevent malicious software and viruses. At the same time, it also designed high-level OS functions to help ensure the security when accessing personal information and company data.

To protect your privacy, applications that get location information from calendars, address books, reminders and photos must first get your permission. You can set a password lock to prevent unauthorized access to your device, and configure it to allow the device to delete all data after multiple failed password entries.

The password will also automatically encrypt and protect your stored email and allow third-party applications to encrypt their stored data. IOS supports encrypted network communication, and app can use encrypted network communication to protect sensitive information during transmission.

If your device is lost or stolen, you can use the Find My iPhone function to locate the device on the map and remotely erase all data. Once your iPhone is restored, you can also restore all the data backed up last time.

Baidu encyclopedia -iOS