How to Secure Linux Server? Ways to Do Hardening in Linux


Do you use Linux servers to deploy your software solutions? Then, securing Linux server setup should be your top priority! If that’s not the case, your server resources are likely vulnerable to cyber attackers. With growing data breaches and cyber threats, you should never overlook your server's security risks!

Consider hardening in Linux server to maximize your server security. Don’t know what Linux server hardening is? Or how to secure your server setting? Consider following the security tips we will be discussing in the coming sections! So, let’s get started!


Why Securing Linux Is Important?


Securing Linux

First, let’s understand why a Linux server is a popular choice for many as a powerful computer system. Linux servers perform excellently when hosting applications and associated services such as databases or web servers. The diversified usage of Linux servers makes it an excellent fit for organizations looking to host their application systems as enterprise environments.

Naturally, the concept of security server Linux arises when an organization chooses a Linux server for hosting. Keep reading to explore why securing your Linux server is crucial:

Prevent Malicious Cyber Attacks: Proactively safeguard your Linux server against DDoS attacks or ransomware through phishing scams.

Protect Sensitive Organizational Data: As Linux databases store sensitive application data, you might lose confidential business information due to data breaches.

Maintain System Integrity: When your Linux setups get compromised, your customers face sudden operational downtime due to system outages.

Enhance Security Architecture: The efficacy of the Linux server hinges on meticulous configuration and proactive management.

Regulatory Compliance Requirements: You must ensure the security server Linux complies with data protection regulations.

So, it’s essential to maintain your Linux server security and ensure business performance continuity. Now, let’s get into the details of Linux hardening and implementing other security strategies to mitigate potential security risks.


What Is Hardening In Linux?


Linux Hardening is a systematic process to secure a VPS server with a Linux-based distribution. It comprises multiple security practices and controls to protect the server infrastructure and safeguard sensitive business data. It also defines how organizations can enforce security policies and configure security parameters to restrict user access.


Linux Security Hardening Checklist: How To Secure A Linux server?


linux server hardening

Now you know about Linux Hardening, it’s time to explore the complete checklist as your definitive guide to setting up security server Linux. Listing here the security best practices tailored for fortifying your Linux server reliability.


1. Use Complex Passwords For Harden Ubuntu Server Security


Still, using a weak Linux server login password for RDP? Most Brute Force attacks happen when the server runs with a weak password. Setting up a solid and unpredictable password is the first step to protect your server from unauthorized user access.

You can use the “passwd root” command to change your Root User password.

Here are organizational guidelines to follow to set a sophisticated server password:

   Use a long password with a minimum of 12 characters

   Use a few upper/lowercase, numerical, and special characters

   Ignore easily guessable words or the server username

   Create a jumbled-up character combination

   Keep updating the password once a month

   Do not repeat a previously used password

Once you harden Ubuntu server with a hard-to-guess password, it becomes impossible for someone to guess it and gain access to your server resources.


2. Disable Root User Login To Secure VPS server


disable root login via ssh

The root user of a Linux server gets complete access to server configurations. He can also make modifications or changes to the Linux Terminal. So, it’s best to disable the Root User access. You can use the following security controls to enforce Root Access limitations:

   Prohibit direct root login via SSH to minimize exposure to brute-force attacks.

   Utilize sudo privileges for executing administrative tasks, enhancing accountability.

   Implement two-factor authentication (2FA) for root access to add another layer of security.

Also, here are the steps to disable Root User Access from the Linux server terminal:

   1. Open the configuration file and run the “nano /etc/ssh/sshd_config” command

   2. Prevent root logins by selecting “no” instead of “yes” for the “PermitRootLogin” parameter

   3. Use the “service ssh restart” command to implement the changes made and save the file.

Once you disable entirely Root User access, nobody will have root privileges to make configuration changes in the secure VPS server.


3. Secure VPS Server By Restricting User Logins


Next, you must restrict server access for other users as well. You might have multiple users in your environment, but that doesn’t mean all users require access to your server. You must authorize access only to server admins. For that, you can use the “AllowUsers” command and edit the sshd_config file with the names of the allowed users. Next, you can do a service restart and reflect the permission changes.

You can also follow these security tips to restrict user access:

   Configure firewall rules to whitelist specific IP addresses

   Implement geolocation-based filtering to allow access from predefined regions

   Deploy IDS solutions to monitor and analyze user login attempts

Following these best practices ensures that only permitted IPs or devices connect to the server.


4. Disable Protocol 1 To Protect Ubuntu Server From Hackers


Disabling Protocol 1 in SSH configurations helps you to enhance the security of your harden Ubuntu server. Protocol 1 is an older SSH version with known vulnerabilities and security weaknesses. Modern SSH implementations prioritize Protocol 2 by default due to its solid encryption algorithm and authentication mechanism.

You can follow these steps to modify your Linux server’s SSH Configuration:

   Modify the SSH configuration file (/etc/ssh/sshd_config) to disable Protocol 1 explicitly.

   Verify the SSH daemon configuration post-modification to maintain Protocol 2 standards.

   Optimize SSH cipher suites to strengthen encryption protocols with secure algorithms.

Finally, you must restart the SSH service and confirm whether the configuration change was successful.


5. Use SSH Non-Standard Ports For Security Server Linux


change ssh port

Lastly, we discussed about disabling SSH Protocol 1. Now, let’s discuss using SSH non-standard ports for hardening in Linux. Using non-standard SSH ports makes it difficult for cyber attackers to identify the correct port number to establish server connectivity. Here are a few security tricks you can try to imply SSH port redirection:

   Modify the default SSH Port 22 to a non-standard port

   Implement port-knocking techniques to obscure unused SSH port accessibility

You can easily change the SSH default port from 22 to 2222 or any other port number as a standalone security measure to protect your Linux server.


6. Use Network Firewall To Filter SSH Connections


As we move on with how to secure a Linux server, the following recommendation is to use a network firewall to filter SSH connections. The firewall acts as an active filter to restrict access based on predefined network rules that allow/deny specific IP addresses to connect to your Linux server.

Here are a few tips for firewall configuration:

   Configure “iptables” or “nftables” rules to filter inbound SSH connections based on predefined criteria.

   Use rate-limiting rules to throttle excessive connection attempts through brute force and DDoS attacks.

   Employ VLANs or subnetting to segregate SSH traffic from general network traffic

These proactive measures effectively block malicious IPs and protect Ubuntu server from hackers. Thus, you can also ensure all your SSH services are accessible only to trusted entities.


7. Use Security Keys For Hardening Debian Linux Server


Employing cryptographic key pairs with security keys is the best way to secure server authentication. This method replaces the password-based authentication approach with encrypted secret keys. As the owner only knows the secret key, no one can further breach the server configurations. Here are a few tips for SSH Key Generation:

   Implement passphrase protection for SSH private keys against unauthorized usage.

   Utilize SSH Key management solutions to centralize key rotation and revocation processes.

   Implement key rotation policies to refresh SSH key pairs periodically.

   Generate RSA or ECDSA SSH key pairs using tools like ssh-keygen with entropy.

Hopefully, you now understand why you should use secret keys to maintain the security server Linux and minimize the chances of brute-force attacks.


8. Keep Your Linux Servers Updated


Linux Servers Updated

Finally, it’s time to discuss the last security best practice for hardening Debian Linux Servers. Always try to keep your servers updated using the following security tips:

   Use a patch management strategy for frequent Linux kernel updates and package upgrades.

   Monitor vendor advisories and security bulletins to remediate vulnerabilities proactively.

   Implement automated server update mechanisms using yum-cron or other systems.

   Conduct periodic vulnerability assessments and penetration tests.


All Set To Protect Ubuntu Server From Hackers?


As we reviewed the Linux security hardening checklist, it’s now clear why securing your Linux server transcends mere technical configurations. So, utilize the security tips and best practices for proactive risk management. Adopt a multifaceted security strategy that safeguards your organizational data and maintains service integrity. So, good luck!