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.

🔒

Confidentiality

Information is only accessible to those authorised to see it. Broken by: eavesdropping, credential theft, data breaches.

✅

Integrity

Data is accurate and hasn't been tampered with. Broken by: man-in-the-middle, SQL injection, ransomware.

🟢

Availability

Systems and data are accessible when needed. Broken by: DDoS attacks, ransomware, hardware failure.

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: