Blacklist a public key

Check the Current SSH Ports

Configure sshd

Configure sshd with multiple authentication factors

Configuring sshd

Disabling sshd

Distribute public keys

Get the host's fingerprint

Install SSH

Limit user logins

Manage SSH Key File With Passphrase

Override socket-activated SSH

Restart SSH

Setup SSH Keys

Test mode

Troubleshooting SSH

Blacklist a public key

Check the Current SSH Ports

Configure sshd

Configure sshd with multiple authentication factors

Configuring sshd

Disabling sshd

Distribute public keys

Get the host's fingerprint

Install SSH

Limit user logins

Manage SSH Key File With Passphrase

Override socket-activated SSH

Restart SSH

Setup SSH Keys

Test mode

Troubleshooting SSH

OpenSSH is the implementation of the SSH protocol on Ubuntu.

OpenSSH is recommended for remote login, making backups, remote file transfer via scp or sftp, and much more. SSH is perfect to keep confidentiality and integrity for data exchanged between two networks and systems.

However, 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 OpenSSH server security:

Before making any modifications to the /etc/sshd_config file, make a backup by:

sudo cp /etc/ssh/sshd_config /etc/ssh/sshd_config.factory-defaults

…and

sudo chmod a-w /etc/ssh/sshd_config.factory-defaults

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.