A ssh server is the most common way to access a server which is connected to the internet. Everybody who knows a userid and password or guesses them can access the server if the standard ssh configuration is used. If he succeeds to get root access the server can be compromized by the attacker and will be used as ftp-server, DOS client, mail SPAM sender ... and the owner of the server is liable for any activities of the attacker. That's awkward and can become quite expensive. The following page describeshow to modify the sshd config file to make the ssh server secure and protectagainst any attacks.

 

Read more: How to protect a ssh server from internet attacks