3.1.9 Provide privacy and security notices consistent with applicable CUI rules.

System use notifications can be implemented using messages or warning banners displayed before individuals log in to organizational systems. System use notifications are used only for access via logon interfaces with human users and are not required when such human interfaces do not exist. Based on a risk assessment, organizations consider whether a secondary system use notification is needed to access applications or other system resources after the initial network logon. Where necessary, posters or other printed materials may be used in lieu of an automated system banner. Organizations consult with the Office of General Counsel for legal review and approval of warning banner content.

Actionable Items: Windows Active Directory Group Policy Editor is a great tool for implementing system-wide policies such as this.

You can purchase an installable GPO with a strong example of the wording here.