If you live in the United States, and depending on which state you live in, if you include the word "welcome" within the MOTD, this can legally be construed as an invitation, which means that anyone can come into the system if they can find a username and password. And since usernames and passwords are transmitted in plain text using telnet or a similar service, you're basically leaving your system open. If someone breaks in, they may not even be prosecutable.
Avoid the use of the word "welcome" in your message; instead use a message that specifically states that only authorized personnel are allowed access to the system. In addition, you'll also want to consider removing operating system information from the MOTD: no need to tell people more about your system then they need to know.
-- SP
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