> So, what are the security modes? In full security mode, new Apple Silicon Macs enjoy the same best-in-class security technologies that exist on iPhone. This mode is enabled by default. In addition, you can now boot from external disk without downgrading the security of the system. We think this is great.
> By contrast, reduced security provides flexibility and configurability of your Mac, and it keeps the Mac what it is.
Reduced security allows you to run any version of macOS, including the versions that are no longer signed by Apple. > In addition, users that want to install notarized kernel extensions must enable this mode in order to do so.
> To enable reduced security, users must authenticate in macOS Recovery first.
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https://developer.apple.com/videos/play/wwdc2020/10686/?time=1078>