Cybersecurity Fundamentals

What Is Cybersecurity?

Cybersecurity (also "information security" or "infosec") is the practice of protecting computer systems, networks, programs, and data from digital attacks, unauthorized access, damage, or theft. As society migrates virtually every aspect of life into digital systems, cybersecurity has become a critical discipline — protecting critical infrastructure, financial systems, personal privacy, and national security.

The CIA Triad defines the three core goals of information security:

🛡️ The CIA Triad

Confidentiality: information is accessible only to those authorized to see it (encryption, access controls).

Integrity: information is accurate and has not been tampered with (hashing, digital signatures, audit logs).

Availability: systems and data are accessible when needed (redundancy, DDoS mitigation, backup strategies).

The Threat Landscape

Malware

Malicious software is the most common attack vector. Key types:

🦠 Viruses & Worms

Viruses attach to files and spread when files are shared. Worms self-replicate over networks without user action. Both can damage files, consume resources, or create backdoors.

🔐 Ransomware

Encrypts victim's files and demands payment for the decryption key. WannaCry (2017) caused $4–8 billion in damages globally. Mitigation: offline backups, network segmentation, patching.

🕵️ Spyware & Trojans

Trojans disguise themselves as legitimate software; spyware silently collects data (keystrokes, passwords, screenshots). Remote Access Trojans (RATs) give attackers full control.

Social Engineering

Attackers exploit human psychology rather than technical vulnerabilities. Phishing (fraudulent emails impersonating trusted entities) accounts for over 90% of successful data breaches. Spear phishing targets specific individuals; whaling targets executives. Vishing (voice phishing), smishing (SMS), and pretexting are related techniques.

Defence: security awareness training, multi-factor authentication, email filtering with SPF/DKIM/DMARC, and a culture where employees feel safe reporting suspicious activity without fear of blame.

Network Attacks

DDoS (Distributed Denial of Service): floods target systems with traffic from many sources (botnets), making services unavailable. Mitigated with CDN/scrubbing services, rate limiting, anycast routing.

Man-in-the-Middle (MitM): attacker intercepts communication between two parties. Mitigated by TLS/HTTPS, certificate pinning, HSTS.

SQL Injection: malicious SQL inserted into user inputs is executed by a poorly coded database layer. Prevented by parameterized queries / prepared statements.

Cross-Site Scripting (XSS): injecting malicious scripts into web pages viewed by other users. Prevented by output encoding, Content Security Policy (CSP), input validation.

Cryptography

Cryptography is the mathematical foundation of security — transforming data so that only authorized parties can read it.

Symmetric Cryptography

The same key encrypts and decrypts. Modern standard: AES (Advanced Encryption Standard) — 128/192/256-bit keys, block cipher. Fast and secure; key distribution is the challenge. Used for encrypting data at rest and in transit (within a TLS session).

Asymmetric (Public Key) Cryptography

Two mathematically related keys: a public key (freely distributed) and a private key (secret). What one key encrypts, only the other can decrypt. RSA (Rivest-Shamir-Adleman) relies on the difficulty of factoring large integers. Elliptic Curve Cryptography (ECC) achieves equivalent security with much smaller keys. Used for key exchange, digital signatures, and TLS certificate authentication.

Hashing

A hash function maps arbitrary data to a fixed-size output (digest). Properties: deterministic, fast to compute, infeasible to reverse, and collision-resistant. Used for password storage (bcrypt, Argon2), file integrity verification, and digital signatures. Never use MD5 or SHA-1 for security purposes — they are cryptographically broken.

E_K(P) = C (encrypt plaintext P with key K to get ciphertext C) D_K(C) = P (decrypt with the same key K)

Authentication and Access Control

Multi-Factor Authentication (MFA) requires at least two factors: something you know (password), something you have (TOTP token, hardware key), something you are (biometrics). MFA stops the vast majority of credential-based attacks — even if a password is compromised, the attacker cannot access the account without the second factor.

Principle of Least Privilege: every user, process, and system component should have only the minimum access required for its function. Limits blast radius if compromised. Implemented via RBAC (Role-Based Access Control) or ABAC (Attribute-Based).

Zero Trust Architecture: never trust, always verify — even inside the corporate network. Every access request is authenticated, authorized, and continuously validated regardless of network location.

Secure Software Development

Security must be integrated across the software development lifecycle (DevSecOps), not bolted on at the end. Key practices:

Input validation: never trust user input — validate type, length, format, and range on the server side.

Parameterized queries: prevent SQL injection by separating SQL code from data.

Dependency management: track and patch vulnerable third-party libraries (SCA tools: Snyk, Dependabot).

Static Analysis (SAST): scan source code for vulnerabilities before it runs.

Secret management: never hardcode credentials — use environment variables or secrets managers (HashiCorp Vault, AWS Secrets Manager).

OWASP Top 10: address the most critical web application security risks: injection, broken authentication, XSS, insecure deserialization, etc.

Try it live

Everything above runs in your browser — open Network Packet Routing and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.