Create the file /var/adm/loginlog, the failed login attempts are going to be logged in this file. It should be created as the root user, and then:
chmod 600 /var/adm/loginlog
chgrp sys /var/adm/loginlog
If the unsuccesful login attempts are bellow 5 for a user account, it would not log, but this can be setup while editing /etc/default/login and [...]
