Welcome to Chapter 5: The Internet and Its Uses!

Hello future Computer Scientists! This chapter is all about the technology we use every single day—the Internet. Understanding how it works is crucial, not just for your exams, but for safely navigating the modern digital world.
Don't worry if terms like 'protocol' or 'DNS' sound confusing. We’ll break them down using simple analogies so you can master these concepts easily!

5.1 The Internet and the World Wide Web

The Great Divide: Internet vs. WWW

Many people use these terms interchangeably, but they refer to two different things. Think of it using a road analogy:

  • The Internet (The Infrastructure): This is the massive, global network of connected hardware (cables, routers, servers, fibre optic lines). It's the physical foundation—like the global highway system.
    (Syllabus Note: The Internet is the infrastructure.)
  • The World Wide Web (WWW or 'The Web'): This is the collection of websites, documents, and resources that are accessed via the Internet using protocols like HTTP. It’s the content or the houses and shops built along the highways.
    (Syllabus Note: The WWW is the collection of websites and web pages accessed using the internet.)

Key Takeaway: The Internet is the hardware connection; the WWW is the content transmitted over that connection.

Understanding the Uniform Resource Locator (URL)

A Uniform Resource Locator (URL) is the text-based address you type into your browser to find a specific resource on the WWW.

A URL has several key parts:

  1. Protocol: E.g., HTTP or HTTPS. This tells the browser how to communicate with the server.
  2. Domain Name: E.g., www.cambridgeinternational.org. This is the readable name that points to a specific web server.
  3. Web Page/File Name: E.g., /syllabuses/cs0478.pdf. This specifies the exact document or file you want to access on that server.
Protocols for Web Communication: HTTP and HTTPS

Protocols are simply sets of rules for communication.

  • Hypertext Transfer Protocol (HTTP): The standard protocol used to transfer web pages and data between the web server and the web browser.
  • Hypertext Transfer Protocol Secure (HTTPS): This is the secure version of HTTP.
    • Purpose and Operation of HTTPS: HTTPS uses encryption (specifically, the secure socket layer (SSL) security protocol) to scramble the data sent between your browser and the server.
    • Why is this important? If you are logging in, shopping, or sending private data, HTTPS ensures that even if a hacker intercepts the data (data interception), they cannot read it.
The Web Browser

The web browser (like Chrome, Firefox, or Safari) is the application software whose main purpose is to render (display) HTML (Hypertext Markup Language) and show you the web page.

Common Functions of a Web Browser:

  1. Address Bar: Allows the user to input the URL.
  2. Navigation Tools: Back, forward, refresh buttons.
  3. Tabs: Allows the use of multiple tabs for different web pages.
  4. History: Records user history (a list of pages previously visited).
  5. Bookmarks/Favourites: Stores frequently visited URLs for quick access.
  6. Storing Cookies: Manages and stores cookie data (more on this below).


Quick Review: HTTP is standard. HTTPS is secure because it uses SSL encryption.

How Web Pages are Located and Retrieved (The Process)

When you enter a URL, a complex process begins involving several key components:

  1. You Enter the URL: The web browser reads the URL (e.g., www.example.com).
  2. DNS Lookup: The browser first needs to find the server's actual location (its IP address). It asks the Domain Name Server (DNS), which acts like the internet's phonebook, to translate the human-readable domain name (example.com) into its unique numerical IP address (e.g., 192.0.2.1).
  3. Request Sent: The browser sends a request (using HTTP/HTTPS) to the newly found IP address.
  4. Server Response: The request reaches the correct web server, which hosts the website files.
  5. Data Transfer: The web server sends the requested page data (usually in HTML format) back across the Internet.
  6. Rendering: The web browser receives the HTML and interprets it, displaying the final formatted web page on your device.
What are Cookies and How are They Used?

Cookies are small text files placed on your computer by a website when you visit it. They are used to save stateful information or track browsing activity.

The Syllabus requires you to know two types and several functions:

  1. Session Cookies: These are temporary. They last only until you close your browser.
  2. Persistent Cookies: These are stored on your device for a specific period (sometimes years).

Common Uses of Cookies:

  • Storing Login Details: Remembering your username and password so you don't have to re-enter them every time.
  • Holding Items in an Online Shopping Cart: If you browse away from the site, the cookie remembers what items you placed in your cart.
  • Tracking User Preferences: Remembering language settings, theme choices, or font sizes.
  • Saving Personal Details: Autofilling forms (like your name or address).

Did you know? Cookies are generally harmless text files, but they are crucial for tracking your behaviour across different websites, which is why many websites now ask for your consent before storing them.

5.2 Digital Currency and Blockchain

This is a newer topic that deals with money in a digital format.

Digital Currency

A digital currency (like Bitcoin or other cryptocurrencies) is money or a medium of exchange that only exists electronically. Unlike physical money, it doesn't have physical coins or notes.

Understanding Blockchain

Digital currencies rely on a system called Blockchain to record transactions securely.

  • Definition: A Blockchain is fundamentally a digital ledger (a record book).
  • Structure: It consists of a series of records (blocks) linked together chronologically using cryptography.
  • Key Feature: It is time-stamped and designed so that the records cannot be altered retroactively. If a transaction is recorded, it is permanent and visible to the network, making it highly secure and transparent.

Analogy: Imagine the Blockchain is a giant, shared notebook where every transaction is written down immediately in permanent ink. Everyone has a copy, so nobody can secretly change an entry.

5.3 Cyber Security

As we rely more on the internet, protecting our data becomes vital. Cyber security involves preventing unauthorised access, use, disclosure, disruption, modification, or destruction of information.

Part 1: Cyber Security Threats

You need to be able to describe the processes involved in a range of security threats and what the attackers aim to achieve.

A. Attacks on Networks and Systems
  • Hacking: Gaining unauthorised access to a computer system or network, usually with the aim of stealing or damaging data.
  • Brute-force attack: A method of gaining access by trying every possible combination of a password until the correct one is found.
  • Distributed Denial of Service (DDoS) attack: Overloading a website or server with a huge volume of traffic from many different computers (often controlled by malware), causing the site to crash or become unavailable to legitimate users.
  • Data Interception: Illegally accessing or monitoring data as it is being transmitted over a network (e.g., sniffing packets).
B. Malware (Malicious Software)

Malware is software specifically designed to disrupt, damage, or gain unauthorised access to a computer system.

  • Virus: A piece of code that replicates itself and attaches to other programs, requiring a human action (like opening a file) to spread. Aim: Damage files.
  • Worm: Similar to a virus but can replicate and spread autonomously across a network without needing a host program or user action. Aim: Consume bandwidth and network resources.
  • Trojan Horse: Software that appears legitimate (e.g., a free game) but contains hidden malicious code. It does not replicate itself. Aim: Create a backdoor for hacking.
  • Spyware: Software that secretly monitors and records a user's activities (e.g., keystrokes, passwords). Aim: Data theft.
  • Adware: Automatically delivers advertisements to a user, often resulting in annoying pop-ups. Aim: Generate revenue for the creator.
  • Ransomware: Locks or encrypts a user's data or system and demands a ransom payment to restore access. Aim: Financial gain.
C. Social Engineering and Deception
  • Social Engineering: Manipulating people into giving up confidential information (e.g., passwords or bank details). This relies on human error rather than technical exploits.
  • Phishing: Sending fake emails or messages pretending to be a reputable source (like a bank) to trick the user into clicking a link or providing personal data.
  • Pharming: Redirecting a user to a fake website, even if they typed the correct URL, usually by manipulating the DNS settings on the user’s computer or server. (It’s more sneaky than phishing because it bypasses checks like checking the URL.)

Quick Review: Malware is software. Hacking is unauthorised access. Phishing/Pharming/Social Engineering target people.

Part 2: Cyber Security Solutions

We use various methods to keep our systems and data safe:


A. Access and Authentication Control
  • Authentication: Verifying the identity of a user before granting access. This typically includes:
    • Username and Password: The most common method.
    • Biometrics: Using unique physical characteristics (e.g., fingerprint or facial recognition).
    • Two-Step Verification (2FA): Requiring a second verification factor after the password (e.g., a code sent to a mobile phone).
  • Access Levels: Limiting what a user can view or edit once logged in. Example: A student might have read-only access to a file, while a teacher has read and write access.
B. Network Protection
  • Firewalls: A security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. It acts as a barrier between a trusted internal network and untrusted external networks (like the Internet).
  • Proxy Servers: A server that acts as an intermediary between a user and the Internet. It can filter content, speed up access by caching pages, and hide the user's IP address, adding anonymity and security.
  • Secure Socket Layer (SSL) Security Protocol: Used to establish an encrypted link between a web server and a browser (forming HTTPS), ensuring all data passed between them remains private.
C. Software and Data Management
  • Anti-malware: Software designed to prevent, detect, and remove malicious software. This includes:
    • Anti-virus: Focuses on finding and removing computer viruses.
    • Anti-spyware: Focuses on finding and removing spyware.
  • Automating Software Updates: Automatically installing patches and updates to fix known security vulnerabilities in operating systems and applications.
D. User Awareness and Privacy
  • Checking the URL Attached to a Link: Hovering over a hyperlink before clicking it to ensure the destination address is legitimate (a defense against phishing).
  • Checking the Spelling and Tone of Communications: Being suspicious of emails that contain poor grammar, spelling mistakes, or an overly urgent tone (a defense against social engineering and phishing).
  • Privacy Settings: Adjusting settings on social media, apps, and browsers to limit the amount of personal data shared publicly or tracked by third parties.

Summary Key Takeaway: Cyber security is a two-part battle: 1) identifying the vast range of threats (from brute-force to ransomware) and 2) applying layered defenses (authentication, firewalls, and anti-malware).