Some server hardening guidelines advised me to add "legal banners" that are visible when you try to log in to a server.
they contain information about how the system is restricted, how only authorized users are allowed in, that it's illegal to enter the system, et c.
it's generally just a way to make it explicitly illegal, so that it'll be harder for people to say "I didn't know I wasn't allowed" if they are prosecuted. it's of course nothing someone would really care about if they wanted to gain entry to a server.
however: what message would scare you off from trying to gain unauthorized entry to a server? what would make you go "I'm not so sure about this", even though you're connected through a VPN and on an ad-hoc live OS?
Kyrillic letters? Moon runes? Honeypot signs? A federal warning?