Cybersecurity Fundamentals

What is Cybersecurity

Cybersecurity is the practice of protecting systems, networks, and programs from digital attacks. These attacks are usually aimed at accessing, changing, or destroying sensitive information; extorting money from users; or interrupting normal business processes.

It encompasses multiple domains including network security, application security, information security, operational security, and disaster recovery. In this course we focus primarily on the network and application layers where the tools you will learn operate.

The CIA Triad

The CIA Triad is the foundational model for information security policy. Every security control exists to protect one or more of these three principles:

Networking Prerequisite

You cannot secure what you do not understand. Every tool in this course operates at the network layer or above. You must understand how data moves across networks before you can analyze, scan, or exploit it.

The OSI Model

The Open Systems Interconnection (OSI) model is a conceptual framework that standardizes network communication into seven layers. Every protocol and device operates at one or more of these layers.

TCP vs UDP

Common Ports & Protocols

Ports are numeric identifiers (0-65535) that distinguish different services on a single host. The first 1024 are "well-known" and reserved by IANA.

IP Addressing & Subnetting

An IPv4 address is a 32-bit number divided into four octets. Subnetting splits a network into smaller segments using a subnet mask.

1# Common CIDR ranges
2/32  = 1 host          (single IP)
3/30  = 4 hosts        (point-to-point)
4/24  = 256 hosts      (small office)
5/16  = 65,536 hosts   (large network)
6/8   = 16,777,216     (massive network)

110.0.0.0    - 10.255.255.255    (10/8)
2172.16.0.0  - 172.31.255.255    (172.16/12)
3192.168.0.0 - 192.168.255.255   (192.168/16)

Essential Terminology

Every field has its vocabulary. Understanding these terms is essential before reading security reports, CVEs, or tool documentation.

The Cyber Kill Chain

Developed by Lockheed Martin, the Cyber Kill Chain describes the stages of a typical cyber intrusion. Defenders try to break the chain at any stage; attackers try to advance through it.

Quick Reference Cheatsheet

Keep this handy. These are the most common commands and concepts you'll use throughout the course.

1# Network discovery
2ping 10.0.0.1          # Test connectivity
3traceroute 8.8.8.8   # Trace network path
4nslookup google.com  # DNS lookup
5whois example.com    # Domain registration
6 
7# File analysis
8file suspicious.exe    # Check file type
9hashdeep file.iso      # Calculate hashes
10strings malware.bin    # Extract strings
11hexdump -C file.bin    # Hex view
12 
13# System info
14uname -a               # System info (Linux)
15ipconfig /all          # Network config (Windows)
16netstat -an            # Active connections

1# CIA Triad
2Confidentiality: Only authorized access (encryption)
3Integrity: Data accuracy (hashes, signatures)
4Availability: Systems up when needed (redundancy)
5 
6# Common attack types
7MITM: Intercept traffic (use encrypted channels)
8DoS: Service unavailable (rate limiting + DDoS protection)
9Phishing: Social engineering (user training + MFA)
10Brute force: Password guessing (rate limiting + lockout)
11 
12# Incident response
131. Identify: What happened?
142. Contain: Stop the spread
153. Eradicate: Remove the threat
164. Recover: Restore systems
175. Lessons learned: Prevent recurrence

How This Course Works

Each tool module follows a consistent learning path designed to take you from zero knowledge to hands-on proficiency. Every module contains concepts, interactive builders, quizzes, and hands-on lab exercises. Ten tools are covered, including Cloudsploit for cloud security scanning.