Dedicated Server Security Checklist:
Complete Linux Server Hardening Guide

SSH Hardening : Beyond Basic Access

SSH is your primary administrative entry point. While moving SSH to a non-standard port reduces log noise from automated scanners, it is not a security feature. Treat it only as a minor filter; it should never replace robust authentication controls to secure dedicated server environments.

Implementing Key-Based Auth and MFA

Action: Disable password authentication entirely in your SSH daemon configuration:

    sudo nano /etc/ssh/sshd_config
# Set these directives:
PermitRootLogin no
PasswordAuthentication no
    
  

MFA Integration: For high-security environments, integrate PAM (Pluggable Authentication Modules) with TOTP via Google Authenticator. This ensures that even if an Ed25519 SSH key is compromised, an attacker still requires a second-factor physical code to enter.

Kernel-Level Visibility & Behavioral Defense

Modern security architecture has shifted from static log parsing to eBPF (extended Berkeley Packet Filter) technology, which monitors system calls directly at the kernel level with near-zero performance overhead.

• Tetragon: Deploy for real-time, kernel-level enforcement and granular observability.


• Falco: The CNCF industry standard for runtime threat detection.


• Tracee: Excellent for tracking process execution and detecting suspicious activity at the syscall layer.

Perimeter & Intrusion Prevention

A strict "Default Drop" policy is the foundation of server firewall best practices.

Configuring Your Firewall

Use ufw or firewalld to restrict access. Ensure your commands are precise to avoid locking yourself out:

    sudo ufw default deny incoming
sudo ufw allow 80/tcp
sudo ufw allow 443/tcp
sudo ufw allow 22/tcp  # Replace 22 with your custom SSH port
sudo ufw enable
    
  

Auditing Open Services

Before finalizing your perimeter defense, verify exactly which services are listening on your network interfaces:

    sudo ss -tulpn
    
  

Intrusion Prevention Systems (IPS)

• Fail2Ban: Highly reliable for basic brute-force prevention. A standard Fail2Ban setup mitigates attacks by parsing system logs and temporarily dropping hostile IPs.
• CrowdSec: A superior, modern approach. As seen in any modern CrowdSec tutorial, this engine can proactively block IPs already identified by its global community network before repeated attacks impact your specific infrastructure.

Web Application Firewall (WAF)

If your dedicated server hosts websites, applications, or APIs, a network firewall is insufficient. You must protect the application layer against threats like SQL Injection, Cross-Site Scripting (XSS), and Path Traversal.

• ModSecurity: The industry-standard open-source WAF, typically paired with the OWASP Core Rule Set (CRS) to aggressively filter malicious HTTP/HTTPS payloads.
• Coraza WAF:A high-performance, extensible WAF engine compatible with ModSecurity rules, ideal for high-traffic, enterprise-grade environments.

Writing Supply Chain & Immutable Infrastructure

• Supply Chain Security: Implement SBOM (Software Bill of Materials) practices. Always verify package signatures (GPG) to ensure the binaries you are installing haven't been tampered with upstream.
• Immutable Infrastructure: Treat your environment as immutable where possible. Using container-native deployments (like Kubernetes) allows you to destroy and redeploy a known-good, hardened state rather than attempting to clean a tainted, persistent system

File Integrity & System Hardening

How do you detect if an attacker has modified core system binaries?

• FIM (File Integrity Monitoring): Tools like AIDE or Wazuh baseline your system and alert you immediately if critical files (like /etc/passwd or /bin/bash) are unexpectedly modified.
• System Auditing: Perform comprehensive system hardening checks utilizing Lynis. This tool acts as an automated security auditor:

    sudo lynis audit system
    
  

• Kernel Hardening: Tune your operating system using sysctl. Modify /etc/sysctl.conf to disable IP forwarding, ignore ICMP broadcast requests, and enable reverse path filtering to prevent IP spoofing attacks.

Maintenance & Disaster Recovery

Automated updates are critical, but Caution: Some core kernel updates require a system reboot. Always schedule these during designated maintenance windows or utilize kpatch for live kernel patching where supported.

• Encrypted Backups: Utilize Restic or BorgBackup for encrypted, incremental, and deduplicated off-site storage. A backup is only valid if it can be restored—conduct dry-run restoration drills quarterly.

Security Automation Reference Matrix

Maintaining Your Infrastructure

Dedicated server security is not a "set it and forget it" task. Effective Linux server hardening requires continuous monitoring, timely patching, stringent authentication protocols, and layered defense mechanisms. By combining SSH hardening, host-level firewalls, intrusion prevention, WAF protection, integrity monitoring, and encrypted off-site backups, organizations can drastically reduce their attack surface and maintain a highly resilient production environment.

Dedicated Server Security at Servers99

At Servers99, we believe security is a shared responsibility. Dedicated servers can be configured with baseline hardening measures such as network filtering, automated patch management, and DDoS mitigation based on deployment requirements.

For advanced users, we provide the flexibility to implement deep security layers like CrowdSec, ModSecurity, and encrypted off-site backups tailored to your specific production workload.

Ready to deploy a secure foundation for your business?