Blacklist scenario: Let's say that a device is detected for fraud/scam activity. I want to blacklist the device for 1 year based on the previously logged-in IP address, so the scammer is no longer able to use their devices. Even though the scammer created a new Firebase account, they won't be able to do that because of the IP address blacklist.

Whitelist scenario: Let's say that I have an internal app. I want this app to be used by my employees only, so only specific devices are allowed to login.