I know that this topic helps prevent USB mount. But there is such thing that while the android mobile is off, volume button + the power button starts the boot, and the android can be still mounted while it is off. How do i prevent this?
volume button + the power button boots the phone either to fastboot mode or recovery mode. One way to do it is to flash a recovery that does not support USB mounting. However, the thief may still flash a new recovery to access your files. At least it would be way more complicated. I'm afraid there is no absolute way to prevent USB mount.