If you want to put a warning message in your own language on Cisco box. Especially it requires 8 bit code. You can change exec-character-bits to 8
Here is how (ex, Korean)
Router# conf t
Router(config)# default-value exec-character-bits 8
Router(config)# banner motd #
enter text message. End with the character "#".
Warning!(??)
Please leave if you are not authorized to be here!
(??? ????)
#
Router(config)# end
Router# exit
Once you re-connect the router, now you will see the Korean banner first on your screen
Warning!(??)
Please leave if you are not authorized to be here!
(??? ????)
password : ***
Router> enable
password : ***
Router#