Securing Linux Servers: Top Strategies for Linux Server Security

Securing Linux servers is a critical responsibility for any organization managing digital infrastructure, especially businesses relying on web hosting in UAE. Whether you are using Ubuntu, Debian, RHEL, or CentOS-based systems, implementing strong Linux server security practices is essential to prevent vulnerabilities, unauthorized access, and system failures.

In regions like the UAE, where businesses rely heavily on digital platforms, even a minor misconfiguration can lead to serious security breaches, downtime, or data loss. This guide covers expert-recommended Linux security best practices while ho, ensuring your server environment remains stable, secure, and optimized.

Why Linux Server Security is Crucial

Linux is widely trusted for its robustness, but improper configuration and lack of maintenance can expose servers to risks such as:

• Unauthorized access
• Malware and rootkits
• Data breaches
• Service disruptions

A properly secured server ensures performance, reliability, and business continuity.

There are different ways to secure Linux-based servers, regardless of whether they run Ubuntu/Debian or RHEL/CentOS.

Keep Linux Kernel and Software Up-to-Date

Keeping your system updated is one of the most fundamental steps in Linux server security.

If the operating system is RHEL or Ubuntu, regularly updating the kernel and installed software helps:

• Eliminate vulnerabilities in outdated packages
• Improve performance
• Enable latest features

Ignoring updates is one of the most common causes of server compromise.

Remove Unnecessary Software

Unused software increases both resource usage and security risks.

Best practice:

• Audit installed packages regularly
• Remove unused modules and applications
• Perform periodic server cleanup

Regular server audits are mandatory to maintain a clean and secure environment.

Disable Unwanted Open Ports

Open ports act as potential entry points for attackers.

Key recommendations:

• Change default SSH port (e.g., use 4422 instead of 22)
• Restrict SSH access to authorized IP addresses only
• Use SFTP instead of FTP

Limiting exposure significantly reduces attack surface.

Linux firewalls are the first line of defense against unauthorized access and malicious activities.  They will regulate incoming and outgoing network traffic based on a set of predefined security rules.

Popular Firewall Options:

Firewalld

• Default in RHEL, CentOS, AlmaLinux, Fedora
• Zone-based rule management
• Easy to manage multiple network connections

Firewalld:

Type: Opensource
UFW (Uncomplicated Firewall):
It is a default firewall tool in Ubuntu based distributions.
Commands are easy to use and understand. 

“Firewalld” is the default firewall in RHEL 7 and later versions, as well as in popular RHEL-based distributions like CentOS, AlmaLinux, and Fedora.

  Firewalld has multiple zones and has its own set of rules, so it’s easy to manage different network   connections

UFW (Uncomplicated Firewall)

• Default in Ubuntu
• Simple and user-friendly commands

iptables

• Advanced firewall configuration
• Uses tables, chains, and rule sets

Proper firewall configuration ensures controlled incoming and outgoing traffic.

 It is used at the traditional level and provides firewall and network traffic management via rule sets. Iptables uses a similar table, chain, and rule structure.

User Accounts with Strong Password Policy

User management is a critical aspect of server security.

Best practices:

• Create only required user accounts
• Assign specific privileges
• Restrict sudo access
• Use strong passwords (minimum 8 characters with uppercase, lowercase, numbers, symbols)

Weak credentials are one of the most exploited vulnerabilities.

Password Aging for User Accounts

Implement password expiration policies to enhance security.

• Use chage command
• Enforce periodic password changes

This reduces risks from compromised credentials.

Disable Root Login

The root user has full system privileges, making it a prime target.

Important steps:

• Disable direct root login
• Use a non-root user with sudo privileges

Ensure a sudo-enabled user exists before disabling root access.

In Linux servers, the root user has super privileges to run all tasks. So if an attacker gains access to it, they can completely compromise your server.

Before disabling the root account, we need to ensure we already have a non-root user with sudo privileges. Without it, you could lose access to critical administrative capabilities.

Hardened Linux Kernel (sysctl.conf)

The /etc/sysctl.conf file controls kernel parameters.

Benefits:

• Prevent IP spoofing
• Mitigate SYN flood attacks
• Enhance network security

 These configurations are applied during system boot.

The /etc/sysctl.conf file contains kernel parameters at runtime. It modifies specific network and system parameters to enhance security and prevent common attacks such as IP spoofing and SYN floods.

The Linux kernel reads and applies the settings from /etc/sysctl.conf during boot.

Use Separate Disk Partitions

Partitioning improves both performance and security.

Recommended partitions:

• /home
• /tmp
• /var

Advantages:

• Prevent system crashes due to full partitions
• Protect user data during OS upgrades
• Improve system stability

Use /etc/fstab for automatic mounting.

It is better to configure the server with separate disk partitions for /home, /tmp, /var/tmp, and related directories.

Because if we mount the site files path, for example, under /home, then if any /tmp disk is full, it will not affect the /home mount path.

Also, it enhances system stability and security and reduces the effort required for reinstallation. A separate /home partition protects the user’s live data during OS upgrades, while a dedicated /var or /tmp partition prevents log files from filling up the root partition and crashing the system.

The /etc/fstab file can be used to ensure partitions mount automatically after rebooting.

Assign Disk Quotas

Disk quotas help control resource usage.

Benefits:

• Prevent disk overuse
• Avoid system crashes due to full storage
• Ensure fair resource allocation

Essential in multi-user environments.

We should assign a specific disk quota to each user to prevent overuse of the server’s disk space and to avoid the disk space from reaching its maximum.

Limit File and Folder Permissions

Proper permissions prevent unauthorized access.

Standard configuration:

• Files → 644
• Folders → 755

Also:

• Set the correct ownership
• Use chattr for advanced control

Misconfigured permissions can expose sensitive data.

We need to set the correct permissions for files (644) and folders (755), and also set proper user and group ownership for the files/folders.

Also, use chattr (change attribute)  to allow users to change the file attributes on a Linux file system.

Disable IPv6 if Not Used

If IPv6 is not required, disable it to reduce the attack surface.

Why?

• Prevent unnecessary vulnerabilities
• Avoid network misconfigurations
• Reduce complexity

Especially useful in isolated or internal environments.

If you are not using IPv6 network we need to disable it.

On the isolated back-end servers, internal infrastructure, or the environments where IPv6 is not routed, then having it enabled adds unnecessary attack surface and can cause confusing network behavior: applications that prefer IPv6 may attempt connections that silently fail, DNS look-ups may return AAAA records that are unreachable, and some security tools need explicit configuration to monitor both protocol stacks.

Proper Logging and Auditing

Monitoring logs is essential for detecting threats.

Key practices:

• Monitor /var/log directory
• Configure logs for web, database, and system
• Enable log rotation

Helps identify attacks and troubleshoot issues efficiently.

The default Linux log directory is “/var/log”. Configuring proper log files for the web server, database server, PHP and server logs, etc. Will be helpful in identifying an attack or any issue on the server.

Also, we need to set up log rotation to a desired value, which will accumulate the log files, and hence, the disk space will be used more.

SSH Hardening

SSH is a common attack vector, so hardening is crucial.

Best practices:

1. Use a custom port number for SSH other than the default port 22
2. Disable direct root login access
3. Use key-based authentication instead of password authentication
4. Disable empty password
5. Limit user access to SSH or SFTP.
6. Restrict IP-based SSH access only from authorised IP addresses

Default config file: /etc/ssh/ssh_config

We need to configure the SSH service with hardened settings, there will be lots of chances of attack through SSH. You need to set the points below in the SSH configuration file.

Webserver Hardening

• Disable the unwanted nginx modules.
• Configure SSL for the nginx or Apache domain
• Disable weak SSL/TLS protocol
• The default state of an Nginx or Apache server returns something like Server: nginx/1.12.1 or Apache in the server response or error pages. The best method is to remove the header completely.
• Set buffer size restrictions for all the clients.

Disable unsafe HTTP methods like TRACE or DELETE

• Configure HTTP security headers
• Regularly update nginx or Apache
• Hide Nginx/ Apache Version Disclosure

Use ClamAV and Chkrootkit or Rkhunter

Recommended tools:

• ClamAV → Antivirus scanning
• Rkhunter → Rootkit detection
• Chkrootkit → Detect hidden threats

Regular scans and updates are essential.

It is suggested to use ClamAV for antivirus scanning and RKHunter (Rootkit Hunter) for rootkit detection, complemented by regular updates and automated scans.

Chrootkit is an open-source rootkit detector that runs locally on Unix-like systems to detect signs of a rootkit. It helps to detect hidden security holes.

RootKit Hunter is a free, open-source, powerful, simple to use, and well-known tool for scanning backdoors, rootkits, and local exploits on POSIX-compliant systems such as Linux.

ClamAV is an open-source, versatile, popular, and cross-platform antivirus engine to detect viruses, malware, trojans, and other malicious programs on a computer.

Backup to secured remote destination

Backups are your last line of defence.

Best practices:

• Store backups remotely
• Automate backups
• Test recovery processes

Ensures business continuity in case of failure.

It is always recommended to take and retain proper backups of the current server data to ensure data is available at remote destinations. So, it will be helpful for restoring the server files in case of any failure.

A server administrator with expert knowledge of managing and auditing the server is needed for the proper, smooth operation of the server.

We are providing server management from its initial setup to monitoring with the support of an expert server team.

A server should be set up properly from scratch; otherwise, it will affect its performance in the future.

Why Expert Server Management Matters

A Linux server should always be managed by experienced professionals. Improper setup from the beginning can create long-term security and performance issues.

From initial setup to continuous monitoring, expert server management ensures:

• Maximum uptime
• Strong security
• Optimized performance

Key Takeaways

• Regular updates prevent vulnerabilities
• Access control is critical
• Monitoring and logging are essential
• Security tools add extra protection
• Backup strategy is non-negotiable

FAQ

What is Linux server security?

Linux server security involves protecting servers from unauthorized access, malware, and vulnerabilities using updates, configurations, monitoring, and access control mechanisms.

Why is firewall configuration important?

Firewall configuration helps regulate incoming and outgoing traffic, preventing unauthorised access and protecting the server from malicious activities.

What is SSH hardening?

SSH hardening involves securing SSH access by using custom ports, key-based authentication, and restricting access to authorized users and IP addresses.

Why should root login be disabled?

Disabling root login reduces the risk of a full system compromise, as attackers cannot gain direct administrative access.

What are the best tools for Linux security?

ClamAV, Rkhunter, and Chkrootkit are widely used tools for detecting malware, rootkits, and hidden threats in Linux systems.

How often should backups be taken?

Backups should be automated and performed regularly (daily or weekly), depending on business requirements.

Implementing strong Linux server security best practices is essential for protecting your infrastructure from modern Cyber threats. By following these expert strategies, businesses in the UAE can ensure secure, stable, and high-performing server environments.

Looking for expert Linux server management in Abu Dhabi or across the UAE?

Get professional support for:

• Server setup & hardening
• Security monitoring
• Performance optimization

Contact our expert team today for reliable server management solutions.

Article by Rojo Jose Rojo Jose is the Founder and CEO of Pentagon Information Technology and a seasoned Digital Strategist with over 29 years of expertise in Cloud Infrastructure & Hosting, Web & E-commerce Development, Cybersecurity, Penetration Testing, and Digital Marketing. With a strong presence across the UAE, US, and UK, he has helped businesses implement secure, scalable, and growth-focused digital solutions. Under his leadership, Pentagon has become a trusted name in delivering innovative IT services worldwide.