NewInstance

There are several files under /etc that enable customization of the login process. For example, in some Countries it is important to warn the user that any activity is monitored to prevent unauthorized use. To do that it’s possible to edit /etc/issue.net as following:

                         -------------
                         W A R N I N G
                         -------------

              THIS IS A PRIVATE COMPUTER SYSTEM.

This   computer   system  including    all  related  equipment,
network  devices (specifically including  Internet access), are
provided  only  for authorized use. All computer systems may be
monitored  for all  lawful purposes,  including to  ensure that
their  use   is  authorized, for management  of the  system, to
facilitate  protection  against  unauthorized  access,  and  to
verify  security   procedures,  survivability  and  operational
security.
Monitoring  includes active attacks by authorized personnel and
their entities to test  or verify the  security  of the system.
During  monitoring,  information  may  be   examined, recorded,
copied   and  used  for  authorized   purposes. All information
including  personal  information, placed  on  or sent over this
system  may be  monitored.  Uses of this system,  authorized or
unauthorized, constitutes consent to monitoring of this system.
Unauthorized  use may  subject  you  to  criminal  prosecution.
Evidence  of  any  such  unauthorized  use   collected   during
monitoring  may be used for administrative, criminal  or  other
adverse action.  Use  of  this  system  constitutes  consent to
monitoring for these purposes.

There’s also a /etc/issue file (without .net extension) that -as I understood- is used for local logins.

When the login is authorized the /etc/motd (message of the day) is displayed. It could be funny to use some random Murphy’s law for this purpose.

A less funny message file is the /etc/nologin that is used to prevent users to login and display some polite message like “System under maintenance, retry later”.

References:

1. Whitepaper: Login Warning Banners A Discussion about Login/Warning Banners, Their Emplacements and Their Uses, Bob Radvanovsky
2. Logon banners for computer systems and network devices, Information Security Team DePaul University