How does the keychain system help protect your information?
Time Machine always ignores temporary files, Spotlight indexes, items in the Trash, log files, and anything else that can be considered a cache. Time Machine also ignores any files an application has defined as exempt, or any files you have defined as exempt in Time Machine preferences.
When fast user switching is enabled, all users are allowed to see other users' locally connected disks.
The keychain system manages encrypted files that are used to securely save your items. By default, every user has login and Local Items keychains that use the same password as his account. Not even other administrative users can access your keychain secrets without knowing the keychain's password.
By default, system files and security updates are automatically installed when available.
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