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====== SSH ======

SSH, or Secure Shell, enables users to connect to a remote server securely.

  * the main advantage is server authentication, through the use of public key cryptography.

Here are a few things you need to tweak in order to improve SSH server security.

<WRAP important>
**IMPORTANT:**  Before making any modifications to the **/etc/sshd_config** file, make a backup by:

<code bash>
sudo cp /etc/ssh/sshd_config /etc/ssh/sshd_config.factory-defaults
</code>

...and

<code bash>
sudo chmod a-w /etc/ssh/sshd_config.factory-defaults
</code>
</WRAP>

<WRAP info>
**NOTE**: Not all of the possible changes mentioned below have to be made.

Some changes are not recommended to be made but may offer tighter security depending on your requirements. 
</WRAP>

----

[[Ubuntu:SSH:Agent forwarding|Agent forwarding]]

[[Ubuntu:SSH:Blacklist a public key|Blacklist a public key]]

[[Ubuntu:SSH:Change the Port|Change the Port]]

[[Ubuntu:SSH:Check the Current SSH Ports|Check the Current SSH Ports]]

[[Ubuntu:SSH:Configure sshd|Configure sshd]]

[[Ubuntu:SSH:Configure sshd with multiple authentication factors|Configure sshd with multiple authentication factors]]

[[Ubuntu:SSH:Configuring sshd|Configuring sshd]]

[[Ubuntu:SSH:Creating public/private key authentication for SSH|Creating public/private key authentication for SSH]]

[[Ubuntu:SSH:Disable SSH root login|Disable SSH root login]]

[[Ubuntu:SSH:Disabling sshd|Disabling sshd]]

[[Ubuntu:SSH:Distribute public keys|Distribute public keys]]

[[Ubuntu:SSH:ERROR - SSH Connection Refused|ERROR - SSH Connection Refused]]

[[Ubuntu:SSH:Get the host's fingerprint|Get the host's fingerprint]]

[[Ubuntu:SSH:Install SSH|Install SSH]]

[[Ubuntu:SSH:Limit user logins|Limit user logins]]

[[Ubuntu:SSH:Manage SSH Key File With Passphrase|Manage SSH Key File With Passphrase]]

[[Ubuntu:SSH:Override socket-activated SSH|Override socket-activated SSH]]

[[Ubuntu:SSH:Port Forwarding|Port Forwarding]]

[[Ubuntu:SSH:Restart SSH|Restart SSH]]

[[Ubuntu:SSH:Setup SSH Keys|Setup SSH Keys]]

[[Ubuntu:SSH:SSH Login Message|SSH Login Message]]

[[Ubuntu:SSH:Test mode|Test mode]]

[[Ubuntu:SSH:Troubleshooting SSH|Troubleshooting SSH]]

[[Ubuntu:SSH:Two-Factor Authentication (using Google Authenticator)|Two-Factor Authentication (using Google Authenticator)]]

[[Ubuntu:SSH:Use SSH without a password|Use SSH without a password]]