Cybersecurity Essentials

Chapter 1 — The CIA Triad

The CIA Triad is the foundational model for information security. Every security control, threat, and attack can be mapped to at least one of its three pillars.

Additional Principles

• Non-repudiation — A user cannot deny an action they performed (digital signatures prove this)
• Authentication — Verifying identity (something you know/have/are)
• Authorisation — What an authenticated user is permitted to do
• Accounting/Auditing — Logging who did what and when

Chapter 2 — Threat Actors

Chapter 3 — Attack Types

Network Attacks

• Reconnaissance — Passive (OSINT, Google dorking) and active (port scanning, ping sweeps)
• Man-in-the-Middle (MitM) — ARP spoofing, SSL stripping, DNS poisoning
• DoS/DDoS — SYN flood, UDP flood, volumetric attacks, application layer (Layer 7)
• Packet Sniffing — Capturing cleartext credentials on unencrypted protocols

Application Attacks

• SQL Injection — Manipulating database queries via unsanitised input
• XSS (Cross-Site Scripting) — Injecting malicious JavaScript into web pages
• CSRF — Tricking authenticated users into performing unintended actions
• File Inclusion — LFI/RFI: including local or remote files through vulnerable parameters
• Command Injection — Executing OS commands via web application input

Social Engineering

• Phishing — Deceptive emails to steal credentials or deliver malware
• Spear Phishing — Targeted phishing using personal information
• Vishing — Phone-based social engineering
• Pretexting — Creating a fabricated scenario to manipulate a target

Chapter 4 — Vulnerability Management

CVE & CVSS

CVE (Common Vulnerabilities and Exposures) is the standardised naming system for known vulnerabilities. Each CVE has an ID like CVE-2021-44228 (Log4Shell).

CVSS (Common Vulnerability Scoring System) scores vulnerabilities 0–10:

# Search CVEs from command line
searchsploit apache 2.4.49
searchsploit -m 50383   # copy exploit to current dir

# Update searchsploit database
sudo searchsploit -u

Chapter 5 — Penetration Testing Methodology

Professional penetration testing follows a defined lifecycle. Every phase feeds information into the next.

Chapter 6 — OWASP Top 10 (2021)

Chapter 7 — Cryptography Basics

Symmetric vs Asymmetric

• Symmetric — Same key encrypts and decrypts. Fast. Key sharing is the problem. Examples: AES-256, ChaCha20, DES (weak)
• Asymmetric — Public key encrypts, private key decrypts. Slow. Solves key distribution. Examples: RSA, ECC, Diffie-Hellman

Hashing

One-way function — input → fixed-length digest. Used for password storage, file integrity, digital signatures. Never encrypt passwords — hash them.

# Generate hashes on Linux
echo -n "password" | md5sum
echo -n "password" | sha256sum
echo -n "password" | sha512sum

# OpenSSL
openssl dgst -sha256 file.txt
openssl rand -hex 32   # generate random key

# Base64 (NOT encryption — just encoding)
echo "hello" | base64
echo "aGVsbG8K" | base64 -d

Chapter 8 — Authentication & Access Control

Authentication Factors

• Something you know — Password, PIN, security question
• Something you have — Hardware token, smart card, phone (OTP)
• Something you are — Fingerprint, face recognition, retina scan

Common Auth Weaknesses

• Default credentials not changed (admin:admin, admin:password)
• No account lockout policy (allows unlimited brute force)
• Weak password policy (minimum 6 chars, no complexity)
• Session tokens predictable or transmitted over HTTP
• Passwords stored in plaintext or weak hash (MD5)

Chapter 9 — Defence Concepts

Defence in Depth

Layer multiple security controls so that if one fails, others still protect the asset. Think: firewall + IDS + endpoint AV + network segmentation + MFA + logging.

Key Defensive Technologies

Chapter 10 — Certifications Roadmap

Certifications validate your skills to employers. Here's a recommended progression for offensive security: