Welcome back, learners! In this detailed guide, we’ll explore Chapter 5 of the IGCSE Computer Science syllabus — all about the Internet, its structure, web technologies, cyber security, and even digital currency and blockchain. Everything here is explained for clear understanding and exam readiness.
5.1 The Internet and the World Wide Web
Internet vs. World Wide Web (WWW)
These two terms are not the same!
| Concept | Description |
|---|---|
| Internet | A global network of interconnected computers. Think of it as the infrastructure. |
| World Wide Web (WWW) | A service on the internet that consists of web pages and websites. Uses HTTP/HTTPS. |
Remember: The internet is the “highway,” and the web is the “traffic.”
URL – Uniform Resource Locator
A URL is the address of a web resource (like a webpage).
Example: https://www.example.com/page.html
https→ Protocolwww.example.com→ Domain name/page.html→ Resource path
HTTP vs HTTPS
| Protocol | Purpose |
|---|---|
| HTTP (HyperText Transfer Protocol) | Used to transfer webpages over the internet. |
| HTTPS (HTTP Secure) | Secure version of HTTP — encrypts data using SSL/TLS. Essential for banking, login, etc. |
🔐 HTTPS ensures data confidentiality and integrity.
Web Browser Functions
A web browser is a software that retrieves and displays web content.
Key Functions:
- Render HTML content
- Store bookmarks/favorites
- Allow multiple tabs
- Save cookies
- Display browsing history
- Provide navigation tools (address bar, back, forward)
✅ Popular browsers: Chrome, Firefox, Safari, Edge
How Web Pages Are Displayed
When you enter a URL, the following happens:
- Browser sends a request.
- DNS (Domain Name Server) translates domain to IP address.
- Browser contacts the web server at that IP.
- HTML content is sent back.
- Browser renders the page.
Cookies
Cookies are small text files stored by the browser to remember user info.
| Type | Purpose |
|---|---|
| Session Cookie | Temporary — deleted when browser closes. |
| Persistent Cookie | Stored long-term — used for logins, preferences. |
🧠 Used For:
- Storing login details
- Keeping items in shopping carts
- Tracking user behavior (ads, analytics)
5.2 Digital Currency and Blockchain
🔹 Digital Currency
- Exists only in electronic form.
- Examples: Cryptocurrencies like Bitcoin, Ethereum.
🔹 Blockchain Basics
A blockchain is a decentralized, digital ledger that stores transactions in blocks.
Characteristics:
- Each block has a timestamp, data, and link to the previous block.
- Cannot be altered once added.
- Transparent and secure.
💡 Use Case: Secure tracking of cryptocurrency transactions.
5.3 Cyber Security
Cyber security is about protecting systems, data, and networks from attacks.
🔹 Common Cyber Threats
| Threat | Description |
|---|---|
| Brute-force attack | Repeatedly guessing passwords until one works. |
| Data interception | Capturing data mid-transmission. |
| DDoS attack | Overloading a server with traffic to shut it down. |
| Hacking | Unauthorized access to systems. |
| Malware | Malicious software (see below). |
| Pharming | Redirecting users to fake websites. |
| Phishing | Fake emails/websites to steal data. |
| Social engineering | Manipulating people into giving up confidential info. |
Malware Types:
- Virus: Attaches to files and spreads.
- Worm: Self-replicates across systems.
- Trojan Horse: Disguised as a legitimate program.
- Spyware: Secretly collects information.
- Adware: Unwanted advertising software.
- Ransomware: Encrypts files and demands payment.
🔹 Cyber Security Solutions
| Solution | Function |
|---|---|
| Firewalls | Block unauthorized access to/from networks. |
| Anti-malware | Detect and remove malicious software. |
| Authentication | User verification via passwords, biometrics, etc. |
| Two-Step Verification | Adds a second verification method (e.g., OTP). |
| Software Updates | Fix security vulnerabilities. |
| Access Levels | Limit user permissions. |
| Privacy Settings | Control what data apps/websites can access. |
| SSL (Secure Sockets Layer) | Encrypts data between browser and server. |
| Proxy Servers | Intermediaries that filter internet access. |
Sample Exam Questions
🧠 1. What is the difference between the internet and the World Wide Web?
✔️ The internet is the network infrastructure; the WWW is a service on the internet consisting of web content.
🧠 2. Explain how a DNS helps load a webpage.
✔️ It translates the domain name into an IP address so the browser can contact the web server.
🧠 3. What is a cookie? Give one example of its use.
✔️ A cookie is a small file stored by the browser; used to save login details or shopping cart items.
🧠 4. Describe two differences between HTTP and HTTPS.
✔️ HTTPS is secure and encrypts data using SSL, whereas HTTP does not. HTTPS is safer for sensitive data.
🧠 5. State two cyber security threats and how they can be prevented.
✔️ Phishing – avoid suspicious links and use email filters. Malware – use anti-virus software.
Summary Table
| Subtopic | Key Takeaways |
|---|---|
| Internet vs WWW | Infrastructure vs content |
| URL & DNS | Addressing and locating webpages |
| HTTP vs HTTPS | Security in data transmission |
| Web Browsers | Rendering and user interface |
| Cookies | Track and store user data |
| Digital Currency | Blockchain-backed electronic money |
| Cyber Threats | Phishing, hacking, malware, DDoS, etc. |
| Cyber Solutions | Firewalls, authentication, SSL, anti-malware |
Final Revision Tips
- Understand how data flows across the internet.
- Be able to explain how websites load, from URL to webpage.
- Learn cookie types and use cases.
- Know malware types and their symptoms.
- Memorize cyber protection methods and when they’re used.
- Understand blockchain logic — what makes it secure.
Below are the slides for this chapter. You can download the presentation to study from slides.