Have you ever had the following error popup on your /var/adm/messages:
Oct 8 12:26:14 myserver sshd[29288]: [ID 800047 auth.error] error: Could not get shadow information for NOUSER
It would look like a security incident with the “nouser” system account but not so to be. The error gets written to /var/adm/messages when a user tries to SSH to the server using a user account which doesn’t exist on the system (a typo error can contribute) or on your NIS/NIS+ systems.
So no panic!!!!