Network Security Fundamentals
You cannot hack a network you do not understand. This guide covers the absolute essentials of networking that every security professional must master. From the packets on the wire to the logical addressing schemes.
Why This Matters
The Two Models You Must Know
OSI Model (7 Layers)
The theoretical framework. Used for discussing attacks.
TCP/IP Model (4 Layers)
The practical implementation. What actually runs.
Mnemonic: "All Traffic Is Not Perfect" (Application, Transport, Internet, Network Access)
Attack Surface by Layer
Every layer presents unique attack opportunities. Knowing where an attack occurs helps you understand how to execute and defend against it.
| Layer | Attack Type | Example Technique |
|---|---|---|
| L7 - Application | Web Exploits | SQL Injection, XSS, API Abuse |
| L4 - Transport | Session Hijacking | TCP Sequence Prediction, SYN Flood DDoS |
| L3 - Network | Routing Attacks | IP Spoofing, ICMP Redirect, BGP Hijacking |
| L2 - Data Link | LAN Attacks | ARP Spoofing, MAC Flooding, VLAN Hopping |
| L1 - Physical | Hardware Attacks | Cable Tapping, Rogue Devices, Jamming |
Quick Reference: Critical Ports
These are the ports you will encounter on almost every engagement. Memorize them.
Learning Modules
Networking Basics
The foundation: OSI Model, IP Addressing, and MAC Addresses.
Protocols & Ports
Understanding TCP/UDP, the 3-Way Handshake, and common services.
Subnetting
Mastering IP division, CIDR notation, and network segmentation.
Essential Recon Commands
Copy-paste these into your terminal to start exploring any network.
nmap -sn 192.168.1.0/24nmap -sT -T4 <target_ip>ip addr show # Linux
ipconfig /all # Windowsarp -atraceroute <target> # Linux
tracert <target> # WindowsRelated Tools
Subnet Calculator
Calculate network ranges, broadcast addresses, and host counts.
Port Reference
Comprehensive list of common and uncommon service ports.
Nmap Command Builder
Interactively build Nmap commands for your scans.
Wireshark Cheatsheet
Filter expressions and analysis tips for packet capture.