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Radhitya Rangga Pratama
Radhitya Rangga Pratama

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Stop Leaving Your Doors Open: 5 Essential Steps for Linux Server Hardening

#security #tutorial #devops #linux

Setting up a server is easy; keeping it secure is a different story. In an era where automated bots scan for vulnerabilities within seconds of a server going live, "default settings" are your biggest enemy. As a security enthusiast at NexxaCodeID, I’ve learned that security isn't just a feature—it’s the foundation.

Here is how I implement Security by Design to harden Linux infrastructure against modern threats.

  1. ##SSH Hardening: The First Line of Defense Your SSH port is the primary target for brute-force attacks. Don't leave the keys under the mat.

Disable Root Login: Never allow direct root access.

Key-Based Auth: Disable password authentication entirely; use Ed25519 SSH keys.

Change Default Port: Moving from port 22 to a custom port (e.g., 2204) cuts down 90% of bot noise.

# Edit /etc/ssh/sshd_config
Port 2204
PermitRootLogin no
PasswordAuthentication no
PubkeyAuthentication yes
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  1. Implement a "Default Deny" Firewall
    The rule is simple: If it’s not required, it’s closed. Use UFW (Uncomplicated Firewall) to drop all incoming traffic except for essential services like HTTPS and your custom SSH port.

  2. Fail2Ban: Automating the Ban Hammer
    Bots are persistent. Fail2Ban monitors system logs and automatically jails IP addresses that show malicious signs (like multiple failed login attempts). It’s a set-it-and-forget-it layer of proactive defense.

  3. Zero-Trust Access with Cloudflare Tunnels
    Industry Standard 2026: Why expose your SSH port to the public internet at all? By using Cloudflare Tunnel (cloudflared), your server doesn't need any inbound ports open. Access is routed through an encrypted tunnel protected by Cloudflare’s Zero Trust dashboard. This makes your server invisible to port scanners.

  4. Automated Security Patching
    Security fails when software rots. Enable unattended-upgrades to ensure critical security patches are applied the moment they are released, without needing manual intervention.

Digital Stewardship: A Christian Perspective
In Cyber Security, we act as stewards of data and privacy. From a Christian ethical standpoint, building secure systems is an act of service—protecting our neighbors' digital lives from those who seek to do harm. Integrity is built when we harden the parts of the system that no one sees, ensuring the safety of those who rely on it.

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