Big Sur - Disable iCloud Address Book

Information

The macOS built-in Contacts.app connection to Apple's iCloud service _MUST_ be disabled.

Apple's iCloud service does not provide an organization with enough control over the storage and access of data, and, therefore, automated contact synchronization _MUST_ be controlled by an organization approved service.

Solution

This is implemented by a Configuration Profile.

mobileconfig profile info:

com.apple.applicationaccess:
allowCloudAddressBook:
False

See Also

https://github.com/usnistgov/macos_security