Restrict user accounts remotely connected through SSH

If you have enabled the Ubuntu SSH service, you can connect to any user with a valid account. This may cause some security problems, because some remote password cracking tools can try common usernames/passwords.

Back up the configuration file of the Ubuntu SSH service

Sudo CP/etc/ssh/sshd_config/etc/ssh/sshd_config.original

Edit configuration file

Sudo gedit/etc/ssh/sshd_config changes the permitrootlogin parameter from yes to No. Super Users cannot directly connect to the Internet through remote connection. Add the allowusers parameter to set the user name for the remote connection (separated by spaces ).
Then Restart sshd.
Sudo/etc/init. d/ssh restart