Step 1: First of all we need to make a regular user, since we are disabling direct root login:

adduser admin && passwd admin

Step 2: Backup your currenct sshd.conf

cp /etc/ssh/sshd_config /etc/ssh/sshd_config.bak

Step 3: Download SecureCentos.com own sshd_config. ( This will overwrite your current config automatic )

wget --output-document=/etc/ssh/sshd_config http://www.securecentos.com/files/sshd/sshd_config

Step 4: Verify settings in the sshd_config you downloaded.

nano -w /etc/ssh/sshd_config

REMEMBER YOU SHOULD CHANGE THE PORT TO SOMETHING ELSE. ( Example Port 2488 )

Step 5.1: Add text to MOTD Banner file (/etc/motd)

nano -w /etc/motd

Step 5.2: Add this text, or something else of your choice

Private system, please log off.

Step 6: Restart the SSHD Daemon

service sshd restart

Step 7: Start a NEW client, and test that you can connect on new port. (DO NOT CLOSE CURRENT SSH CLIENT INCASE OF PROBLEMS)

Extra layer of security, under development :) Using DSA Keys to authenticate user.

Step 1: Create folders, generate 1024Bits DSA key

mkdir ~/.ssh && chmod 700 ~/.ssh && cd ~/.ssh && ssh-keygen -t dsa -f ~/.ssh/id_dsa

cat id_dsa.pub >> ~/.ssh/authorized_keys && rm -Rf id_dsa.pub && chmod 600 ~/.ssh/*

Its recommended to use PASSPHRASE on your keys, incase someone gets access to your keys.

Step 2 Copy DSA Private key "id_dsa" to your client computer
Step 2.1: Copy file to Windows client

SFTP or FTP it to your computer

Step 2.2: Copy file to Linux client

scp ~/.ssh/id_dsa username@clientcomputer:~/.ssh/id_dsa

Step 2.3: When your done, delete the id_dsa file from server

rm -Rf ~/.ssh/id.dsa

Step 3: How to setup Putty to use the Server Private Key
Step 3.1: Download a program named puttygen to convert openssh keys to puttykeys, HERE
Step 3.2: Use puttygen, Choose Load -> Find openssh Key -> Find File -> Enter Passphrase if needed
Step 3.3: Change Comment field to smart
Step 3.4: Save private Key, etc servername.pkk

Use the tool pageant to list your keys, and putty will use them automatic, download HERE

Troubleshooting:

Some dedicated server companyes have small iptables script running at server initiation, so you may have to run the command "iptables --flush" if you change the sshd port.