Chapter 5: The Internet and Its Uses - [2210/0478] IGCSE/GCE CS Notes

Based on Cambridge Syllabus 2026-2028

The Internet and the World Wide Web

Internet vs World Wide Web

These two terms are often used interchangeably, but they mean different things.

Concept	Description
Internet	A global network of interconnected computers. This is the physical infrastructure (cables, routers, servers).
World Wide Web (WWW)	A service on the internet that consists of web pages and websites. This is the content you access.

Simple Analogy:

The internet is the highway system (roads, bridges, traffic lights)
The World Wide Web is the traffic (cars, trucks, buses) using the highways

Key Difference

The internet is the infrastructure that connects devices globally
The World Wide Web is a collection of information (web pages) accessed via the internet

Other services that use the internet (but are NOT the web):

Email (SMTP, POP3)
File transfer (FTP)
Online gaming
Video conferencing (Zoom, Skype)

URLs and Web Addresses

What is a URL?

URL stands for Uniform Resource Locator. It is the text-based address used to locate a web page or resource on the internet.

Example URL:

https://www.example.com:443/products/page.html?id=123#section2

Structure of a URL

Component	Example	Purpose
Protocol	`https://`	Rules for communication between browser and server
Subdomain	`www`	Specific section of the website (optional)
Domain Name	`example.com`	Human-readable name of the website
Port	`:443`	Specific gateway on the server (optional)
Path	`/products/page.html`	Specific file or page location
Query String	`?id=123`	Additional parameters (optional)
Fragment	`#section2`	Specific part of the page (optional)

Breaking Down a Simple URL

https://www.cambridge.org/education/subject/computer-science
│      │               │               │
│      │               │               └── Path (specific location)
│      │               └── Domain name (website name)
│      └── Subdomain (often www)
└── Protocol (how to communicate)

Domain Name System (DNS)

DNS translates human-readable domain names (like google.com) into IP addresses (like 142.250.185.46) that computers understand.

Think of DNS as the phonebook of the internet.

HTTP and HTTPS Protocols

What is a Protocol?

A protocol is a set of rules that determines how data is transmitted between devices.

HTTP (Hypertext Transfer Protocol)

HTTP is the protocol used to transfer web pages over the internet.

Characteristics:

Used for communication between web browsers and web servers
Requests web pages and sends them back
Not secure – data is sent in plain text

HTTPS (HTTP Secure)

HTTPS is the secure version of HTTP. It encrypts data using SSL/TLS.

Characteristics:

Same functions as HTTP
Adds encryption layer (SSL/TLS)
Data is scrambled and unreadable if intercepted
Essential for sensitive information (banking, logins, payments)

Comparison: HTTP vs HTTPS

Feature	HTTP	HTTPS
Security	None – data in plain text	Encrypted using SSL/TLS
Port	Port 80	Port 443
Padlock icon	No	Yes (in browser address bar)
Data confidentiality	No	Yes
Data integrity	No	Yes
Authentication	No	Yes (verifies website identity)
Use cases	Public information	Banking, shopping, logins

Why HTTPS Matters

Confidentiality: Prevents eavesdropping on your data
Integrity: Ensures data hasn’t been tampered with during transmission
Authentication: Confirms you’re connected to the real website, not a fake

Web Browsers

What is a Web Browser?

A web browser is software that retrieves, renders, and displays web pages from the internet.

Popular browsers: Chrome, Firefox, Safari, Edge, Opera

Main Purpose of a Web Browser

The primary purpose of a web browser is to render HTML (Hypertext Markup Language) and display web pages in a user-friendly format.

Key Functions of a Web Browser

Function	Description
Render HTML	Interprets HTML code and displays it as formatted web pages
Address Bar	Allows user to enter URLs to visit specific websites
Navigation Tools	Buttons for Back, Forward, Refresh/Reload, Home
Multiple Tabs	Open several web pages simultaneously in one window
Bookmarks/Favourites	Save links to frequently visited websites
History	Records previously visited websites for easy access
Cookies	Stores small text files to remember user information
Download Manager	Manages files downloaded from the internet
Privacy Features	Incognito/private browsing, clear history, delete cookies
Extensions/Add-ons	Additional features added by third-party developers

Browser Interface Components

┌─────────────────────────────────────────────────────┐
│ [←] [→] [↻]  [https://www.example.com]  [🔍] [⋮]  │
├─────────────────────────────────────────────────────┤
│                                                     │
│                                                     │
│                 WEB PAGE CONTENT                    │
│                   RENDERED HERE                      │
│                                                     │
│                                                     │
└─────────────────────────────────────────────────────┘

How Web Pages are Located and Displayed

Step-by-Step Process

When a user enters a URL into a browser, the following happens:

User enters URL: https://www.example.com/page.html

      ↓

1. Browser checks cache for DNS record
      ↓
2. Browser asks operating system for DNS lookup
      ↓
3. DNS server translates domain to IP address
      ↓
4. Browser establishes connection to web server
      ↓
5. Browser sends HTTP/HTTPS request
      ↓
6. Web server processes request and finds page
      ↓
7. Web server sends back HTML content
      ↓
8. Browser receives HTML and begins rendering
      ↓
9. Browser requests additional resources (CSS, images)
      ↓
10. Page is fully rendered and displayed

Detailed Explanation

Step 1-3: DNS Lookup

Browser needs to find the IP address of the web server
Checks local cache first (browser cache, OS cache)
If not found, asks a DNS server
DNS server returns the IP address (e.g., 93.184.216.34)

Step 4-5: Connection and Request

Browser connects to the web server at that IP address
Sends an HTTP request asking for the specific page
Request includes information like browser type, accepted formats

Step 6-7: Server Response

Web server finds the requested HTML file
Sends it back to the browser with a status code (e.g., 200 OK)
If page not found, sends 404 error

Step 8-10: Rendering

Browser receives HTML and starts parsing
Builds the Document Object Model (DOM) structure
Requests any additional files (CSS for styling, images, JavaScript)
Assembles and displays the complete web page

Key Components Involved

Component	Role
Web Browser	Sends requests, receives and renders HTML
DNS Server	Translates domain names to IP addresses
Web Server	Stores web pages and sends them to browsers
IP Address	Unique numerical identifier for each device
HTML	Language used to structure web page content

Cookies

What are Cookies?

Cookies are small text files stored on a user’s device by a web browser when they visit a website. They contain information about the user’s activity on that site.

Purpose of Cookies

Cookies are used to:

Remember user preferences
Keep users logged in
Track items in shopping carts
Personalise content and ads
Analyse website traffic

Types of Cookies

Type	Description	Duration	Examples
Session Cookies	Temporary cookies that exist only while browser is open	Deleted when browser closes	Shopping cart items during a single visit
Persistent Cookies	Remain on device after browser closes	Set expiration date (days/months/years)	Login details, language preferences

Session Cookies

Characteristics:

Stored in temporary memory
Deleted when user closes the browser
No expiration date set
Used for single-session activities

Uses:

Keeping items in a shopping cart during one visit
Remembering what page you were on
Tracking form progress

Persistent Cookies

Characteristics:

Stored on hard drive
Remain after browser closes
Have an expiration date
Used for long-term preferences

Uses:

“Remember me” login functionality
Language preferences
Website theme choices
Tracking user behaviour over time

Common Cookie Uses

Use Case	Cookie Type	Explanation
Login details	Persistent	Keeps you logged in between visits
Shopping cart	Session	Remembers items while browsing the site
Language preference	Persistent	Shows site in your preferred language
Analytics	Persistent	Tracks how you use the site
Advertising	Persistent	Shows relevant ads based on browsing

Privacy Concerns

Cookies can track browsing habits across websites
Third-party cookies track users for advertising
Privacy laws (like GDPR) require websites to ask for cookie consent

Digital Currency

What is Digital Currency?

Digital currency is money that exists only in electronic form. It has no physical equivalent (no coins or notes).

Examples:

Cryptocurrencies (Bitcoin, Ethereum)
Central Bank Digital Currencies (CBDCs)
E-money (PayPal balance,支付宝)

Characteristics of Digital Currency

Feature	Description
Electronic only	No physical form
Decentralised (cryptocurrencies)	Not controlled by banks or governments
Peer-to-peer	Can be sent directly between users
Global	Works across borders
Secure	Uses cryptography to prevent fraud

How Digital Currencies are Used

Online purchases – Buy goods and services
Investment – Buy and hold as investment
Money transfers – Send money across borders cheaply
Payments – Pay for transactions without banks

Blockchain

What is Blockchain?

Blockchain is a digital ledger (record book) that stores transactions in a series of blocks. Each block is linked to the previous one, forming a chain.

Think of it as a shared, unchangeable record book that everyone can see but no one can alter.

Structure of a Blockchain

Block 1 (Genesis)          Block 2                   Block 3
┌──────────────┐          ┌──────────────┐          ┌──────────────┐
│ Block Header │          │ Block Header │          │ Block Header │
│ • Timestamp  │◄────────►│ • Timestamp  │◄────────►│ • Timestamp  │
│ • Previous   │          │ • Previous   │          │ • Previous   │
│   Hash: 0    │          │   Hash: 7B3  │          │   Hash: 9F2  │
│ • This Hash: │          │ • This Hash: │          │ • This Hash: │
│   7B3        │          │   9F2        │          │   D4E        │
├──────────────┤          ├──────────────┤          ├──────────────┤
│ Transactions │          │ Transactions │          │ Transactions │
│ • Tx 1       │          │ • Tx 4       │          │ • Tx 7       │
│ • Tx 2       │          │ • Tx 5       │          │ • Tx 8       │
│ • Tx 3       │          │ • Tx 6       │          │ • Tx 9       │
└──────────────┘          └──────────────┘          └──────────────┘

Key Characteristics of Blockchain

Characteristic	Description
Decentralised	No single authority controls it
Immutable	Once data is added, it cannot be changed
Transparent	All transactions are visible to participants
Time-stamped	Each block has a timestamp
Cryptographically secured	Uses complex maths to ensure security

How Blockchain Tracks Digital Currency Transactions

Transaction occurs – Person A sends 1 Bitcoin to Person B
Transaction is verified – Network computers check if Person A has sufficient funds
Added to a block – Transaction grouped with others into a block
Block is added to chain – New block permanently linked to previous blocks
Transaction complete – Record is now permanent and unchangeable

Why Blockchain is Secure

No central point of failure – Copies exist on many computers
Cannot alter past blocks – Changing one block would require changing all subsequent blocks
Cryptographic hashing – Each block has a unique fingerprint
Consensus mechanism – Network agrees on valid transactions

Cyber Security Threats

Cyber security is about protecting systems, networks, and data from digital attacks.

Common Cyber Security Threats

Threat	Description
Brute-force attack	Repeatedly trying different passwords until one works
Data interception	Capturing data while it’s being transmitted
DDoS attack	Overwhelming a server with traffic to make it unavailable
Hacking	Gaining unauthorised access to computer systems
Malware	Malicious software designed to cause harm
Pharming	Redirecting users to fake websites without their knowledge
Phishing	Tricking users into revealing sensitive information
Social engineering	Manipulating people to give up confidential information

Detailed Explanation of Each Threat

Brute-force Attack

Process: Automated software tries millions of password combinations
Aim: Gain unauthorised access to accounts
Prevention: Strong passwords, account lockout after failed attempts, CAPTCHA

Data Interception

Process: Attacker captures data as it travels across networks
Aim: Steal sensitive information (passwords, credit card details)
Prevention: Encryption (HTTPS, VPN), secure networks

Distributed Denial of Service (DDoS) Attack

Process: Multiple compromised computers flood a server with traffic
Aim: Make the service unavailable to legitimate users
Prevention: Firewalls, traffic filtering, DDoS protection services

Hacking

Process: Exploiting vulnerabilities to gain unauthorised access
Aim: Steal data, cause damage, or use system for other attacks
Prevention: Strong authentication, regular updates, firewalls

Malware Types

Malware is any software intentionally designed to cause damage.

Type	Description	How it Spreads
Virus	Attaches to legitimate programs and replicates	Infected files, downloads
Worm	Self-replicates across networks without user action	Network vulnerabilities
Trojan Horse	Disguised as legitimate software	Fake downloads, email attachments
Spyware	Secretly monitors and collects information	Bundled with other software
Adware	Displays unwanted advertisements	Bundled with free software
Ransomware	Encrypts files and demands payment for decryption	Phishing emails, infected downloads

Social Engineering and Deception-Based Threats

Phishing

Process: Sending fake emails pretending to be legitimate organisations
Aim: Trick users into revealing passwords, credit card details
Example: Email claiming to be from your bank asking you to verify account

Pharming

Process: Redirecting users to fake websites even if they type correct address
Aim: Steal login credentials
Method: DNS poisoning, malicious code on computer

Social Engineering

Process: Manipulating people through psychological tricks
Aim: Gain confidential information or access
Examples: Pretending to be IT support, impersonating colleagues

Cyber Security Solutions

Range of Solutions to Protect Data

Solution	Description
Access Levels	Limiting what users can see and do
Anti-malware	Software to detect and remove malicious programs
Authentication	Verifying user identity
Software Updates	Fixing security vulnerabilities
Checking Communications	Verifying emails and links before clicking
Firewalls	Blocking unauthorised network access
Privacy Settings	Controlling what information is shared
Proxy Servers	Intermediaries that hide your identity
SSL/TLS	Encrypting data in transit

Detailed Explanation of Each Solution

Access Levels

Users only have permission to access what they need
Examples: Read-only access, admin privileges restricted
Prevents: Unauthorised access to sensitive data

Anti-malware (including Anti-virus and Anti-spyware)

Scans files and programs for known malware signatures
Monitors system behaviour for suspicious activity
Removes or quarantines detected threats
Requires regular updates to recognise new threats

Authentication Methods

Method	Description	Examples
Username and Password	Something you know	Traditional login
Biometrics	Something you are	Fingerprint, face recognition
Two-step verification	Two different methods	Password + code sent to phone
Multi-factor authentication	Multiple methods	Password + biometric + security key

Automating Software Updates

Updates often contain security patches
Automatic updates ensure protection is current
Reduces window of vulnerability

Checking the Spelling and Tone of Communications

Phishing emails often contain spelling mistakes
Urgent or threatening language is suspicious
Verify sender email address carefully

Checking the URL Attached to a Link

Hover over links to see actual destination
Look for misspelled domain names (e.g., go0gle.com)
HTTPS does not guarantee site is legitimate

Firewalls

Monitors incoming and outgoing network traffic
Blocks unauthorised access based on security rules
Can be hardware or software based
Prevents: Unauthorised access, some DDoS attacks

Privacy Settings

Controls what information apps and websites can access
Limits data collection and sharing
Examples: Location services, camera access, ad personalisation

Proxy Servers

Acts as intermediary between user and internet
Hides user’s real IP address
Can filter content and block malicious sites
Provides anonymity

Secure Socket Layer (SSL) Security Protocol

Encrypts data between browser and server
Creates secure, encrypted connection
Indicated by HTTPS and padlock icon
Prevents: Data interception, eavesdropping

Matching Threats to Solutions

Threat	Solution
Brute-force attack	Strong passwords, account lockout, two-step verification
Data interception	SSL/HTTPS, encryption
DDoS attack	Firewalls, traffic filtering
Hacking	Firewalls, authentication, access levels
Malware	Anti-malware, software updates
Phishing	Checking emails/URLs, authentication
Pharming	Check URLs, use trusted DNS
Social engineering	User education, verification procedures

Summary & Key Takeaways

Internet vs WWW

Internet	World Wide Web
Infrastructure	Service
Network of networks	Collection of web pages
Hardware	Content

URL Components

Protocol://Domain:Port/Path?Query#Fragment

HTTP vs HTTPS

HTTP	HTTPS
No encryption	Encrypted (SSL/TLS)
Port 80	Port 443
Not secure	Secure

Web Browser Functions

Render HTML
Address bar
Navigation tools
Multiple tabs
Bookmarks
History
Store cookies

How Web Pages Load

URL → DNS Lookup → Connect to Server → Request Page → Receive HTML → Render

Cookies

Session	Persistent
Temporary	Permanent until expiry
Deleted on close	Stored on device
Single visit	Across visits

Digital Currency & Blockchain

Digital currency: Electronic only money
Blockchain: Unchangeable digital ledger
Characteristics: Decentralised, immutable, transparent

Cyber Security Threats

Threat	What It Does
Brute-force	Guesses passwords
Data interception	Captures transmitted data
DDoS	Overwhelms servers
Hacking	Unauthorised access
Malware	Malicious software
Pharming	Redirects to fake sites
Phishing	Fake emails/websites
Social engineering	Manipulates people

Cyber Security Solutions

Solution	What It Does
Access Levels	Limits permissions
Anti-malware	Detects/removes malware
Authentication	Verifies identity
Software Updates	Fixes vulnerabilities
Check communications	Identifies scams
Firewalls	Blocks unauthorised access
Privacy settings	Controls data sharing
Proxy servers	Hides identity
SSL/HTTPS	Encrypts data

Practice Questions

Section A: Internet and WWW

Explain the difference between the internet and the World Wide Web.
Give two examples of internet services that are NOT the World Wide Web.

Section B: URLs and Protocols

Label the components of this URL: https://www.school.com:443/students/year10/page.html?id=45
What is the purpose of a DNS server?
State two differences between HTTP and HTTPS.
Why is HTTPS important for online banking?

Section C: Web Browsers

List four functions of a web browser.
What does it mean when we say a browser “renders HTML”?
Name three popular web browsers.

Section D: How Web Pages Load

Describe the steps that occur when a user types a URL into a browser and presses Enter.
What role does the web server play in displaying a web page?

Section E: Cookies

What is a cookie?
Explain the difference between session cookies and persistent cookies.
Give three examples of how cookies are used on websites.

Section F: Digital Currency and Blockchain

What is digital currency?
Describe what a blockchain is.
Explain two characteristics of blockchain that make it secure.
How does blockchain track digital currency transactions?

Section G: Cyber Security Threats

Describe each of the following cyber security threats:
a) Brute-force attack
b) Phishing
c) DDoS attack
d) Ransomware
Explain the difference between a virus, a worm, and a Trojan horse.
What is social engineering? Give an example.

Section H: Cyber Security Solutions

Describe how each of the following helps protect data:
a) Firewall
b) Anti-malware software
c) Two-step verification
d) SSL/HTTPS
Why are automatic software updates important for security?
How can users protect themselves from phishing attacks?
What is the purpose of a proxy server?

Quick Reference Card

Topic	Key Points
Internet	Physical network infrastructure
WWW	Collection of web pages
URL	Protocol + Domain + Path
HTTP	Port 80, not secure
HTTPS	Port 443, encrypted
DNS	Translates domain to IP
Browser	Renders HTML, tabs, bookmarks, history
Session cookie	Temporary, deleted on close
Persistent cookie	Stored, has expiry date
Digital currency	Electronic only
Blockchain	Unchangeable digital ledger
Brute-force	Guessing passwords
Phishing	Fake emails
DDoS	Overload with traffic
Malware	Virus, worm, Trojan, spyware, ransomware
Firewall	Blocks unauthorised access
Anti-malware	Detects and removes
SSL/HTTPS	Encrypts data
Two-step verification	Two authentication methods

End of Chapter 5: The Internet and Its Uses

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