Top 10 Linux Server Security Tips

There are many tools and methodologies to safeguard servers from illegal access and other cyber threats. It is essential for system administrators and cyber-security teams to secure the servers correctly. Most users consider Linux a great system to have a highly secure system. 

To keep your servers functioning safely and effectively, you must still follow best practices. However, as a beginner or intermediate user, it can become tough to handle security-related aspects. So if you also want to know the Top 10 Linux Server Security Tips, this guide is for you.

1. Ensure the Essentials 

Creating a strong password and enabling two-factor authentication are the first steps to securing any system. A password must contain at least ten characters, including special characters and letters (lowercase or uppercase). For different users or software systems, use separate passwords. Change the password in a specific period because no password can provide adequate protection indefinitely. 

Multiple password managers, like BitWarden, LastPass, Enpass, Dashlane, etc., are available to secure and sync the password. However, a single password manager is perfect for every server. Therefore, it’s critical to choose the correct one according to your requirements. 

2FA offers an extra layer of security and immediately eliminates the risk of password compromise. You can use 2FA with Secure Shell (SSH) to enforce the needs of the second credential at the login phase. Therefore, 2FA and a strong password can develop resistance to brute force attacks and unauthorized logins and improve the safety of the server. 

2. Create a Pair of SSH Keys

Passwords can help, but there are other ways to log into private servers that are considerably more secure. Secure Shell (SSH) key pairs are recommended for deployment since they make brute force hacking more difficult.

It’s crucial to understand why you might wish to use SSH keys instead of the traditional username and password setup before using them. While passwords are more convenient for familiar users, these same individuals often rely on readily guessed choices, exposing the entire security infrastructure.

SSH key pairs are significantly more secure than passwords while being less user-friendly. This improved security can be because of the encryption used by both the server and the computer. In the simplest terms, an SSH key pair is the equivalent of a 12-character password. Therefore, when implementing a proactive server security policy, ensure that you use SSH key pairs.

3. Keep the System Up-to-Date

Make sure you check for regular updates to keep the Linux server secure. New patches can address newly discovered vulnerabilities to evaluate security flaws. Unfortunately, many Linux users cannot implement these updates. As a result, the server can become vulnerable and easy to hack. Consider automating the process if you’re having trouble keeping up with the required security updates. 

Enable automatic updates that will allow the system to keep everything stays up-to-date. Sometimes, automatic updates download unnecessary patches, so please check out the updates while implementing the new update. 

It is essential to update the server regularly to avoid security breaches and unauthorized access. Moreover, try to update the content management system, plugins, and other add-on functionalities as every new patch come with security issues fixes. 

4. Remove All Unnecessary Software

Although installing new software is appealing, not all online services are essential. You can add different packages to extend the functionalities, which is good. Once you install any package, then it gains access to your server. However, adding more packages, software, and third-party repositories can lead to higher vulnerabilities for the server. It is necessary to remove all unnecessary packages and software to secure the Linux server. 

The necessary tools may cause significant security risks in the long run. Perform a system-wide software and cyber-security audit at least once a year. This simple commitment can improve your server and keep running at optimal efficiency even when adding new apps. You can use an RPM (Red Hat Package Manager) to review recently installed items.

5. Check and Close the Open Port

Open ports may reveal network architectural information while extending attack surfaces. Attackers can exploit these types of vulnerabilities to access the server. To take it down one step further, block the unused ports to avoid any new service binding to them.

It would be best to find out the open ports and close them as soon as possible. You can use netstat commands that list the incoming connections. Once you find any open port, then close it immediately to secure the server. 

6.  Turn off External Device Booting

Malicious users can readily use external devices like USB drives to access critical information. Disabling external device booting can reduce physical attacks, which can be just as dangerous as hacking. Anyone can readily bypass many security layers without this extra step. Hence, make sure you turn off all external devices booting to keep the server secured. 

7. Security Audits are Important

While the tips listed above can help you feel more secure as you work to strengthen the security server, new dangers could emerge at any time. Even the most secure server will become vulnerable to new threats if it is not updated correctly. Of course, software upgrades are essential, but security audits can reveal other worthwhile improvements. 

It’s hard to know where gaps exist or how to close them so that your server remains fully protected without regular audits. That’s why you must conduct security audits regularly to avoid all security-related issues from the Linux server.

8. Create and Maintain Backups Regularly

Backups are essential to keep any system secure. With backups, you can restore crucial data in case any incursion occurs on the server. In Linux, the application Rsync is a popular choice for data backup. It includes several options that enable you to create daily backups or exclude particular files from being duplicated. 

It is well-known for its versatility, making it an excellent choice for a wide range of Linux server security tactics. Moreover, backups work best if you test them regularly. Testing ensures that backups contain the correct (and most recent) files and that you can quickly recover them in data loss. 

9. Enable Firewall

The firewall can secure the system from unauthorized access. Hence, it is good to inspect the firewall to ensure the server’s security. iptables offer a fantastic way to filter all outgoing, incoming, and forwarding IP packets. 

You can create Allow and Deny rules for accepting or sending traffic from a particular IP address. These rules restrict unauthorized traffic or any movement on the server. Nowadays, DDoS (Distributed Denial of Service) attacks are becoming common and can become a threat to the server. That’s why enabling a firewall can protect your system from DDoS attacks.  

10. Use SELinux

SELinux, also known as Security-enhanced Linux, is a fantastic security architecture for Linux. It allows a server admin to control and access the system. SELinux uses different security policies to understand any server’s accessible and accessible points. 

When a user (subject) tries to access any file (object), SELinux checks the access through AVC ( Access Vector Cache), where all permissions are cached for a subject and object. Hence, it is good to implement SELinux and use it to protect the Linux server from any third-party attack. 

Enforcing and Permissive are two different modes for SELinux. Enforcing is the highly secured mode that enforces all the policies to enhance security. The Permissive mode in SELinux does not enforce the server policy but logs and audits the activities. 

Security is Always Essential

Securing your Linux server with extra effort can go a long way. Remember that Linux hardening and server security is a continuous process that causes regular audits, software patches, and data backups. Your efforts to stay on top of these requirements could save you a lot of headaches.

Spend some time developing a more vital password strategy and learning a few fundamental security procedures. You’ll have a more powerful server that can avoid some of today’s most dangerous security threats.