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Configuring Port Knocking with Knockd on Linux: A Practical Guide to Stealth SSH

By IT From Zero October 20, 2026

Completely hide your SSH port from botnets and automated network scanners using Port Knocking. A step-by-step guide to configuring Knockd with Iptables and ~/.ssh/config on production Linux systems.

Security

How to Install and Configure Suricata IDS/IPS on Linux: Real-Time Network Traffic Monitoring and Intrusion Prevention

By IT From Zero October 19, 2026

A detailed comparison of passive IDS and inline IPS architectures for Suricata on Linux. Learn how to configure Suricata with NFQUEUE, tune rulesets, and test real-time threat prevention.

Network

Configuring Transparent Proxy with TPROXY on Linux: Redirecting All TCP/UDP Without Per-Client Configuration

By IT From Zero July 9, 2026

TPROXY is a Linux kernel mechanism that intercepts and redirects all TCP/UDP traffic before clients can react — smart TVs, IP cameras, and IoT devices are intercepted without knowing it. From a 5-minute quick start to production-ready setup with nftables, SSL bump, and a practical debug checklist.

Network

XDP Linux: Building an Ultra-Fast Packet Filter at the Driver Layer to Block DDoS

By IT From Zero July 2, 2026

XDP (eXpress Data Path) processes and filters packets directly at the NIC driver layer — before they enter the kernel stack — making it 10 to 100 times faster than iptables. This guide covers everything from writing an eBPF program in C, compiling and loading it into the kernel, to managing a real-time IP blocklist with BPF Maps and Python.

Security

Building an Incident Response Process for Linux Servers: Investigation, Containment, and Recovery After an Attack

By IT From Zero June 13, 2026

A practical guide to building a Linux Server Incident Response process using the PICERL model: from confirming an incident and emergency network isolation, to collecting evidence, eradication, and safely restoring the system. Includes real commands drawn from hands-on production incident experience.

Security

Moving from iptables to nftables: Why It’s a Mandatory Step for SysAdmins

By IT From Zero April 22, 2026

Iptables is outdated and slow. Discover how nftables optimizes firewall performance, supports IPv4/IPv6 simultaneously, and how to safely migrate your Linux system.

Network

Port Knocking: How to Hide SSH Ports and Make Your Linux Server Invisible to Botnets

By IT From Zero April 18, 2026

Port Knocking is a security technique that completely hides SSH ports from port scanners. Learn how to install knockd on Linux to protect your server from brute-force attacks.

Network

Basic Linux Router Setup: Guide to Configuring NAT and Packet Forwarding

By IT From Zero March 18, 2026

A detailed guide on how to transform a Linux machine into a basic router. This article will walk you through configuring Network Address Translation (NAT), including Masquerading and Port Forwarding, along with enabling Packet Forwarding, providing practical commands and clear explanations to help you build and manage your network effectively.

Ubuntu

Configuring Fail2ban to Protect Your Ubuntu Server from Brute-Force Attacks

By IT From Zero March 6, 2026

Fail2ban automatically blocks brute-force IPs targeting SSH, Nginx, and WordPress by reading logs and adding iptables rules. This guide covers installation, practical jail configuration, and common troubleshooting scenarios on Ubuntu 22.04.

Linux

Configuring a Firewall with iptables on Linux: A Production-Ready Script for Web Servers

By IT From Zero March 4, 2026

A production-ready iptables script for web servers: chains and tables structure, SSH rate limiting, locking down MySQL and Redis, and how to persist rules across reboots. Includes a tip to avoid locking yourself out during testing.