This may help, but you will have to masage it to your liking copy the whole thing and enter it at the commandline of the juniper device and commit the configuration.
set system login message or
set system login announcement "\n\n\n\n################################################################\n\n\n\nt\n\n## |.-;`\..../`;_.-^-._ You have accessed a restricted ##\n## /\\/ / |...::..|` : : `| device. It is for official and ##\n\\## |:'\ | /'''::''| .:.:. | authorized use only. You have ##\n## \ /\;-,/\ :
.:::.:::.| no expectation of privacy in ##\n## |\ <` > >._::_.| '::.::' | its use. To ensure that the ##\n\\## | `""` / ^^ | ':.:' | device is functioning properly ##\n## | | \ :.: / individuals using this system ##\n## | | \ : : / are subject to having all of ##\n## | |___/\___|`-.:.-` their activities monitored and\n## | \_ || _/ recorded.\n\n\n##############################################################\n\n\n\n"
If the message text contains any spaces, enclose it in quotation marks.
You can format the message using the following special characters:
- \n—New line
- \t—Horizontal tab
- \'—Single quotation mark
- \"—Double quotation mark
- \\—Backslash