CISA has identified nine factors that entities should consider as they develop banners that provide notice to employees of network monitoring and seek their consent. There is one set of guidance for state, local, tribal and territorial governments, and another set of guidance for private sector entities.
This link provides the standard banner language used within the Department of Defense along with a list of FAQs.
This whitepaper from SANS discusses elements of a logon banners specific to the United States.
This video shows administrators how to configure a logon banner using Group Policies in Active Directory.
This video focuses on implementing an Interactive Message Before Login feature.
This video shows administrators how to configure a logon banner in Cisco IOS for routers and switches