open registry and locate for System under Policies
(Computer\HLM\Software\Microsoft\Windows\CurrentVersion\Policies\System).
Make sure you backup the System registry folder before making changes.
i) Right Click from System folder and Select New – String Value. Name it as legalnoticecaption. DoubleClick to modify the Value Data and name it Legal Notice.
ii) Right Click from System folder and Select New – String Value. Name it as legalnoticetext. DoubleClick to modify the Value Data and enter the following text:
This Computer System and Network is sole property of your company name full (companyshortname) and may be used only by companyshortname employees for official purposes. Any sort of unauthorized use of this system is strictly prohibited and may be subject to criminal prosecution. Users should have no expectation of privacy as to any communication on or information stored within the companyshortname systems and network. The companyshortname reserves the rights to monitor any activity or communication on the system and retrieve any information stored within the system. By accessing and using this computer and network, you are consenting to such monitoring and information retrieval for law enforcement and other purposes.
this can be very well be added at domain security policy level.