Information
An access warning informs the user that the system is reserved for authorized use only, and that the use of the system may be monitored.
Rationale:
An access warning may reduce a casual attacker's tendency to target the system. Access warnings may also aid in the prosecution of an attacker by evincing the attacker's knowledge of the system's private status, acceptable use policy, and authorization requirements.
Impact:
If users are not informed of their responsibilities, unapproved activities may occur. Users that are not approved for access may take the lack of a warning banner as implied consent to access.
Solution
Perform the following to enable a login banner set to your organization's required text:
Graphical Method:
Open System Preferences
Select Security & Privacy
Select Show a message when the screen is locked
Select Set Lock Message
Insert text in the Set a message to appear on the lock screen that matches your organization's required text
Terminal Method:
Run the following command to enable a custom login screen message:
$ sudo /usr/bin/defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText '<custom.message>'
example:
$ sudo /usr/bin/defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText 'Center for Internet Security Test Message'
Profile Method:
Create or edit a configuration profile with the PayLoadType of com.apple.loginwindow
Add the key LoginwindowText
Set the key to '<Your organization's required text>