Please look at this auth.log (from Ubuntu 14.04) I have provided and tell me who this gdm user is and why there are all these unauthenticated logins? I am freaked out; please help! Here's the /var/log/auth.log file: http://paste.ubuntu.com/8120231/ Update: I know now that "gdm" is gnome desktop manager and it's there because of root. But please look at the log there is more and tell me if my system is breached.