The main reason why you may need to disable the system abort sequence (Stop+A) could be security of your system. Anybody who can abort the system and bring it to OBP can eventually try to gain access to the root user account. You can disable the system abort sequence (Stop+A) in several different ways.
By default, in Solaris, the owner of the file cannot use the chown command to change the owner of the file or directory. There is also restriction in using chgrp command. The owner can only use chgrp command to change the group of the file to a group, which the owner belongs to. However, this [...]
You can control root access to the system by setting parameters in the /etc/default/login file. The /etc/default/login file establish default parameters for users when they log in to the system.
I guess there are two ways how to get quick overview over users of the system. First one is to check /etc/shadow file and second one is by using logins command.
You can save failed login attempts by creating /var/adm/loginlog with read and write (600) permissions for root user only. Loginlog file does not exist by default.