#Webmin authentication failures from /var/log/auth.log

#1 User exists, bad password
Dec 13 08:15:18 sb1 webmin[25875]: Invalid login as root from 89.2.49.230 

#2 User does not exists
Dec 12 23:14:19 sb1 webmin[22134]: Non-existent login as robert from 188.40.105.142