What is the purpose of the External Boot setting in the Startup Security Utility?

The External Boot setting in the Startup Security Utility is designed to allow or restrict the ability of the Mac to boot from external media. When this setting is enabled, users can boot the system from alternative sources such as external drives, USB flash drives, or network volumes. This can be particularly useful for troubleshooting, installing operating systems, or using recovery tools.

When the setting is disabled, the device will only boot from the internal startup disk, which enhances security by preventing unauthorized or potentially malicious external media from being used to start the computer. This security feature helps maintain the integrity of the boot process and protects against certain types of attacks that might involve booting from compromised external media.