Source: http://www.howtogeek.com/121650/how-to-secure-ssh-with-google-authenticators-two-factor-authentication/ Also, for CentOS: http://www.tecmint.com/ssh-two-factor-authentication/ Want to secure your SSH server with easy-to-use two-factor authentication? Google provides the necessary software to integrate Google Authenticator’s time-based one-time password (TOTP) system with your SSH server. You’ll have to enter the code from your phone when yo..
Check the server if it is root compromised. lsattr /usr/bin Root compromised output. All of those files are set to immutable and append only. That’s what the “ia” you see is. [root@mail ~]# lsattr /usr/bin s—ia——- /usr/bin/bzcmp s—ia——- /usr/bin/getkeycodes s—ia——- /usr/bin/enc2xs s—ia——- /usr/bin/mail-files s—ia——- /usr/bin/chage s—ia——- /usr/bin/mdeltree s—ia——- /usr/bin/nslookup s—ia——- /usr/bin/semodule_link s—ia——- /usr/bin/mbchk s—ia——- /usr/bin/rpcgen ..