How To Harden Centos

How To Articles

As a seasoned system administrator, I have had my fair share of experiences with securing CentOS servers. In this article, I will guide you through the process of hardening CentOS and share some personal insights and commentary along the way.


CentOS is a popular and reliable operating system for servers, but out of the box, it may not offer the strongest security posture. By implementing some additional measures, you can significantly improve the security of your CentOS server and protect it against potential threats.

Securing Remote Access

One of the first areas to address when hardening CentOS is securing remote access. By default, CentOS allows SSH access for remote administration, which makes it essential to take the necessary steps for secure remote access:

  1. Change the default SSH port: Attackers often target SSH on the default port (22). Changing the default port number can help deter automated scanning and brute-force attacks.
  2. Restrict SSH access to specific IP addresses: By configuring CentOS’s firewall to only allow SSH connections from trusted IP addresses, you can limit access to your server.
  3. Implement public key authentication: Instead of relying solely on passwords, using public key authentication adds an extra layer of security to SSH connections. It ensures that only users with the corresponding private key can access the server.

Updating and Patching

Keeping your CentOS server up to date is crucial for maintaining a secure environment. Regularly applying updates and patches ensures that you benefit from the latest security fixes and improvements. To automate the process, you can use yum-cron, which automatically checks for updates and installs them.

Securing Services

Hardening the services running on your CentOS server is essential to minimize potential vulnerabilities. Here are some tips to help secure commonly used services:

Web Server (Apache or Nginx)

When securing your web server:

  • Disable or remove unnecessary modules: Reducing the attack surface by disabling or removing unnecessary modules can help improve the security of your web server.
  • Implement SSL/TLS encryption: Enabling HTTPS with a trusted SSL/TLS certificate ensures secure communication between the server and clients, protecting sensitive data.
  • Utilize secure HTTP headers: Set strict HTTP headers to protect against common web vulnerabilities, such as cross-site scripting (XSS) and clickjacking.

Database Server (MySQL or PostgreSQL)

Securing your database server is crucial to safeguarding your data:

  • Change default database credentials: Ensure that you change the default usernames and passwords for your database server to prevent unauthorized access.
  • Implement strong database user permissions: Grant only the necessary permissions to database users to limit their access and reduce the risk of unauthorized actions.
  • Enable database encryption: Encrypting sensitive data at rest adds an extra layer of protection, especially if the server is compromised.


Hardening a CentOS server requires a proactive approach towards security. By implementing the steps outlined in this article, you can significantly enhance the security posture of your CentOS server and protect it from potential threats. Remember to regularly review and update your security measures to stay ahead of emerging risks.