Linux Tactic

Secure Your Remote Server with SSH Two-Factor Authentication

SSH Protocol and Two-Factor Authentication: How to Secure Your Remote ServerInformation technology has become an indispensable aspect of our lives. Whether for work or personal use, we rely on devices and networks to connect us to the world.

With this connectivity, however, comes the risk of security breaches. Organizations, as well as individuals, face the risk of cyber-attacks, which can lead to enormous financial and reputational losses.

Among the most common attack vectors is the SSH protocol, which is used to connect to remote servers. In this article, we will discuss how implementing two-factor authentication can enhance the security of SSH connections.

We will also provide a step-by-step guide on how to configure two-factor authentication on a Fedora 30 system.

Benefits of Using Two-Factor Authentication

Traditional authentication typically involves providing a user ID and a password to access a service or device. However, this method is not foolproof as passwords can be easily compromised, either through theft or brute-force attacks.

Therefore, use two-factor authentication to add an extra layer of security. Two-factor authentication requires a user to provide not only a password but also a verification code.

This code is typically generated by an authenticator app that runs on a mobile device. The app is synchronized with the service, and a new code is generated every 30 seconds.

Using two-factor authentication makes it much more difficult for an attacker to gain access to a remote server, as they will need both the user’s password and their mobile device. This greatly reduces the likelihood of an unauthorized access attempt.

Authenticator Applications for Mobile Devices

The most popular authenticator apps for mobile devices are Google Authenticator for Android devices, and Apple IOS devices. To use an authenticator app, you simply need to download and install it on the mobile device, and then synchronize it with the service you want to secure.

Once connected, the app generates a 6-digit verification code every 30 seconds, which is required to gain access to the service.

Setup Overview

To set up two-factor authentication on your Fedora 30 system, you will need to install the Google-Authenticator app, which generates the verification codes. Once installed, you will need to configure the SSH daemon to require two-factor authentication for remote logins.

Finally, you will configure your SSH client to use two-factor authentication when connecting to the remote server.

Installation and Configuration on Fedora 30

Installing Google-Authenticator

To install Google-Authenticator on a Fedora 30 system, you can use the following command:

sudo dnf install google-authenticator

This will install the app along with its dependencies.

Running Google-Authenticator

Once installed, you can run the app using the terminal on your local machine. The app generates a QR code, which you can scan using the authenticator app on your mobile device.

The app also generates a set of scratch codes, which you can use in case the mobile device is lost, or the app is otherwise unavailable.

Finishing the Configuration

After configuring the mobile device using the authenticator app, you need to configure the SSH daemon. Open the /etc/ssh/sshd_config file and add the following lines:

ChallengeResponseAuthentication yes

AuthenticationMethods publickey,keyboard-interactive

The first line will enable challenge-response authentication for SSH connections, while the second line specifies the authentication methods that will be used. You should also configure rate-limiting to prevent brute-force attacks.

Add the following lines to the file:

MaxAuthTries 3

MaxSessions 2

This will limit the maximum number of attempts that can be made before the user is locked out. Finally, restart the SSH daemon using the following command:

sudo systemctl restart sshd.service

Accessing the Remote Server with SSH and Two-Factor Authentication

To access the remote server, you will need to use the ssh command with the -o flag. The -o flag specifies the authentication method to be used.

For example:

ssh -o PreferredAuthentications=password,keyboard-interactive user@remotehost

This command specifies that both password and two-factor authentication should be used.


By implementing two-factor authentication for SSH connections, you can significantly increase the security of your remote server. This article has provided an overview of the SSH protocol, as well as information on how to configure two-factor authentication on a Fedora 30 system.

By following the steps outlined in this article, you can enhance the security of your remote connections, protecting your critical data and systems from unauthorized access. In conclusion, implementing two-factor authentication for SSH connections is essential for enhancing the security of remote servers.

By adding an extra layer of security, two-factor authentication makes it much more difficult for attackers to gain unauthorized access. The article has highlighted the benefits of two-factor authentication, the use of authenticator apps, and the step-by-step process of configuring two-factor authentication on a Fedora 30 system.

The takeaway is that implementing two-factor authentication is a powerful tool in securing your remote server, and it is essential for anyone who wants to protect their critical data and systems from unauthorized access. Remember, taking proactive steps towards preventing security breaches is key to safeguarding your digital infrastructure.

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