Linux Server Security: 15 Steps to Take After Installation

When you set up a new Linux server, the default configuration is inadequate from a security standpoint — root SSH access is open, the firewall is disabled, and unnecessary services are running. Linux server security steps taken immediately after installation dramatically increase your server's resistance to attacks. This guide covers 15 critical security steps from SSH hardening to fail2ban setup, firewall configuration to automatic updates.

SSH Security and Hardening

SSH is the primary tool for server management and one of the most targeted services. In default configuration, direct root login is possible and brute force attacks on port 22 are constant. Your first step should be hardening the SSH configuration.

SSH Security Checklist

✓

Disable Root Login: Set PermitRootLogin no and create a sudo-enabled user instead.
✓

Use SSH Key Authentication: Disable password login (PasswordAuthentication no) and allow only SSH key access.
✓

Change SSH Port: Move from default port 22 to block automated scanning bots.
✓

Restrict Allowed Users: Use the AllowUsers directive to permit only specific users SSH access.

💡 Tip: When generating SSH keys, prefer the Ed25519 algorithm — it provides the same security level as RSA with shorter key sizes and is faster. Generate with ssh-keygen -t ed25519.

Firewall Configuration

Use UFW (Uncomplicated Firewall) or iptables to open only necessary ports. Set the default policy to deny all incoming traffic and open only SSH, HTTP (80), and HTTPS (443) ports. Database ports (3306, 5432) should never be exposed externally.

Step	Description	Priority
SSH Hardening	Disable root, key auth, port change	🔴 Critical
Firewall Setup	Port control with UFW/iptables	🔴 Critical
Fail2ban Setup	Brute force attack prevention	🔴 Critical
Auto Updates	Automatic security patch application	🟡 High
Log Monitoring	Suspicious activity detection	🟡 High

Brute Force Protection with Fail2ban

Fail2ban monitors log files and automatically blocks IP addresses after a specified number of failed login attempts. It provides ready-made filters for SSH, Nginx, Apache, and other services. Even with default settings, it blocks the vast majority of brute force attacks targeting your server.

⚠️ Important: Don't forget to whitelist your own IP address when setting up fail2ban. Otherwise, you might accidentally lock yourself out of the server. Add your static IP or VPN IP range to the ignoreip setting.

For more on Linux server security, check CIS Benchmarks guides and the Fail2ban documentation.

Frequently Asked Questions

Are these steps necessary if I use managed hosting?

Managed hosting providers handle basic security configuration, but application-level security remains your responsibility. Learn which security measures your provider implements and fill in the gaps yourself.

Does changing the SSH port really improve security?

Port changes are considered "security through obscurity" and aren't sufficient alone. However, 99% of automated scanning bots target only port 22. Combined with SSH key authentication and fail2ban, port changes form an effective additional layer.

Are automatic updates risky on production servers?

Automatically applying security updates is far less risky than not updating at all. Configure unattended-upgrades for security updates only. Schedule maintenance windows for kernel updates that require restarts.

For SSL configuration, read our SSL/TLS Certificate Guide. For DDoS protection, check our DDoS Protection Strategy article. For WAF setup, see our WAF and ModSecurity Guide.

Security-Focused Managed Server Solutions

SSH hardening, firewall configuration, and 24/7 security monitoring included with managed server solutions to keep your infrastructure safe.

Explore Cloud Server Plans →