Introduction
Cyber Security protects computer systems, networks, and data from digital attacks. This chapter covers
the different types of malicious software (malware), common attack methods, and the defensive tools used
to counter them.
Types of Malware
| Type | Behaviour |
|---|
| Virus | Attaches itself to a legitimate program/file; requires user action (running the infected file) to spread and activate |
| Worm | Self-replicating; spreads across networks WITHOUT needing to attach to a host file or user action |
| Trojan Horse | Disguises itself as legitimate software to trick users into installing it; does not self-replicate |
| Ransomware | Encrypts a victim's files and demands payment (ransom) for the decryption key |
| Spyware | Secretly monitors and collects user activity/information without consent |
| Adware | Automatically displays unwanted advertisements |
| Rootkit | Grants unauthorised privileged access while hiding its own presence |
📌 Virus vs Worm — Key Distinction: A virus needs a host file and user action to spread; a worm is independent and self-propagating across networks — a frequently tested conceptual distinction.
Common Cyber Attack Methods
| Attack | Description |
|---|
| Phishing | Fraudulent emails/messages tricking users into revealing sensitive information (passwords, card details) |
| Denial of Service (DoS/DDoS) | Overwhelms a system/server with traffic, making it unavailable to legitimate users |
| Man-in-the-Middle (MITM) | Attacker secretly intercepts and possibly alters communication between two parties |
| SQL Injection | Malicious code inserted into a database query to manipulate/access unauthorised data |
| Brute Force Attack | Systematically trying every possible password combination to gain access |
| Spoofing | Disguising communication (email, IP address) to appear as if from a trusted source |
Defensive Measures
| Measure | Function |
|---|
| Firewall | Monitors and filters incoming/outgoing network traffic based on security rules — acts as a barrier between trusted and untrusted networks |
| Antivirus Software | Detects, quarantines, and removes malware from a system |
| Encryption | Converts data into a coded form (ciphertext) that can only be read with the correct decryption key |
| Two-Factor Authentication (2FA) | Requires two independent forms of verification (e.g., password + OTP) for login |
| VPN | Virtual Private Network — creates an encrypted, secure connection over a public network |
Encryption Basics
| Type | Description |
|---|
| Symmetric Encryption | Same key used for both encryption and decryption |
| Asymmetric Encryption | Uses a public key (encryption) and a private key (decryption) — the basis of HTTPS/SSL security |
Cyber Laws in India
📌 Information Technology Act, 2000: India's primary cyber law legislation, providing legal recognition for electronic transactions and penalties for cybercrimes like hacking, data theft, and identity fraud — subsequently amended (notably in 2008) to address evolving cyber threats.
✅ UPSC/SSC Focus: Malware type distinctions (virus vs worm vs trojan vs ransomware) · Common attack methods (phishing, DDoS, SQL injection) · Firewall vs antivirus vs encryption roles · Symmetric vs asymmetric encryption · IT Act 2000 as India's cyber law framework.