Year 11 · Computer Science · Autumn 2

The internet and its uses · Lesson 5 of 5

Exam questions and the scenario question

Exam practice5.1 The internet and the World Wide Web5.3 Cyber security7.9 Writing and amending algorithms

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

You will learn to

  • Answer past-paper questions on topic 5 within the time allowed.
  • Use the mark scheme to find the exact words that earn each mark.
  • Plan and write a scenario question answer, then mark it.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Success criteria

You have got it when you can say:

  • I can finish the topic 5 questions in the time given.
  • I can rewrite one lost-mark answer so it would earn full marks.
  • I can tick off each scenario requirement I met on the mark scheme.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Retrieval starter

Questions from before. Write your answers, then show them.

  1. Last lesson

    A DDoS attack…

    A Floods a server with requests from many machinesB Encrypts your files for moneyC Guesses passwords

    A. Floods a server with requests from many machines

  2. Last unit

    An interrupt is…

    A A loop that never endsB A signal that makes the CPU pause and deal with somethingC A type of virus

    B. A signal that makes the CPU pause and deal with something

  3. Earlier this unit

    Each block in a blockchain contains…

    A A hash of the previous block, so any change showsB A pictureC Only a password

    A. A hash of the previous block, so any change shows

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Key words (1 of 9)

Internet
The worldwide network of connected computer networks: the physical infrastructure.
World Wide Web (WWW)
The collection of websites and web pages that are reached using the internet.
URL
Uniform resource locator: the text address of a web page, made of protocol, domain name and file name.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Key words (2 of 9)

HTTP / HTTPS
The rules for sending web pages; HTTPS adds encryption using SSL.
Web browser
Application software that fetches web pages and renders HTML so you can see them.
DNS
Domain Name System: servers that find the IP address that matches a domain name.
IP address
A number that identifies a device on a network, such as 151.101.0.81.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Key words (3 of 9)

Cookie
A small text file a website stores on your device to remember you.
Digital currency
Money that exists only electronically.
Brute-force attack
Trying every possible password or key until the right one is found.
DDoS
Distributed denial of service: flooding a server with requests from many computers so real users cannot reach it.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Key words (4 of 9)

Malware
Software designed to cause harm, such as a virus, worm, Trojan horse, spyware, adware or ransomware.
Phishing
A fake message that tricks the user into clicking a link and giving personal details on a fake site.
Pharming
Malicious code or a tampered DNS server redirects the user to a fake website, even if they type the correct URL.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Key words (5 of 9)

Social engineering
Manipulating people into breaking normal security rules.
Firewall
Hardware or software that checks traffic in and out against rules and blocks anything that breaks them.
Proxy server
A server between the user and the internet that filters requests, hides the user's IP address and caches pages.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Key words (6 of 9)

SSL
Secure Sockets Layer: a protocol that uses certificates and encryption to secure data between browser and server.
Algorithm
A precise, ordered set of steps that solves a problem.
Program development life cycle
The four stages of making a program: analysis, design, coding and testing.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Key words (7 of 9)

Structure diagram
A top-down diagram that shows how a system is split into sub-systems.
Pseudocode
A structured, code-like way of writing an algorithm that is not tied to one language.
Totalling
Adding values into a running total, for example Total ← Total + Value.
Counting
Adding 1 to a counter each time something happens.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Key words (8 of 9)

Bubble sort
Sorting by comparing neighbouring items and swapping them if they are in the wrong order, pass after pass.
Validation
An automatic check that input data is reasonable and follows set rules.
Verification
A check that data has been copied or typed in exactly as the original.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Key words (9 of 9)

Check digit
An extra digit calculated from the other digits, used to catch typing errors.
Normal data
Test data that should be accepted.

5.1 The internet and the World Wide Web · The explanation · step 1 of 25 · part 1 of 3

The internet is not the same as the web

The internet is the physical network. It is millions of computers, cables, routers and wireless links joined together across the world. It is the infrastructure.

The World Wide Web (WWW) is a collection of websites and web pages stored on computers connected to the internet.

The web is one service that uses the internet. Email, online gaming and video calls also use the internet, but they are not the web.

5.1 The internet and the World Wide Web · The explanation · step 1 of 25 · part 2 of 3

The internet is not the same as the web (continued)

InternetWorld Wide Web
What it isA global network of networks (hardware and connections)A collection of web pages and websites (information)
Made ofCables, routers, servers, wireless linksPages written in HTML, linked by hyperlinks
UsesWeb, email, video calls, file transfer, online gamesViewing web pages in a browser
ProtocolsTCP/IP and many othersHTTP and HTTPS

5.1 The internet and the World Wide Web · The explanation · step 1 of 25 · part 3 of 3

The internet is not the same as the web (continued)

e.g.Example
Think of the Madrid Metro. The tunnels, tracks and stations are the internet. The trains carrying people to places are like services. The web is one line on that network; email is another.
!Watch out

Do not use the two words as if they mean the same thing. The internet is the network. The web is the pages.

5.1 The internet and the World Wide Web · The explanation · step 2 of 25 · part 1 of 4

The parts of a URL

A URL (uniform resource locator) is the text address of a web page. It is what you type into the address bar.

Cambridge splits a URL into three parts: the protocol, the domain name and the web page/file name.

The protocol is the set of rules used to transfer the page, such as `https`. The domain name names the web server, such as `www.bbc.co.uk`. The web page/file name is the exact page or file on that server, often with a folder path before it.

5.1 The internet and the World Wide Web · The explanation · step 2 of 25 · part 2 of 4

The parts of a URL (continued)

Part of the domainMeaning
wwwThis is a web server
bbcThe organisation's name
.co.ukTop-level part: a company in the UK (others: .com, .org, .es, .gov)

5.1 The internet and the World Wide Web · The explanation · step 2 of 25 · part 3 of 4

The parts of a URL (continued)

e.g.Example
https://www.bbc.co.uk/news/technology.html Protocol: https Domain name: www.bbc.co.uk Path (folder): /news/ Web page/file name: technology.html Try it in the toy: type this URL to see its parts. Then press Step to follow the DNS lookup and the request.

5.1 The internet and the World Wide Web · The explanation · step 2 of 25 · part 4 of 4

The parts of a URL (continued)

?Why?

People remember names far more easily than numbers. The URL is a human-friendly label; DNS later turns the domain name into the server's IP address.

!Watch out

The protocol is not "www". The protocol is the part before `://`, such as `http` or `https`.

There is something to try for this step in the IGCSE library.

5.1 The internet and the World Wide Web · The explanation · step 3 of 25 · part 1 of 2

HTTP and HTTPS

HTTP (Hypertext Transfer Protocol) is the set of rules for sending web pages between a web server and a browser.

HTTPS (Hypertext Transfer Protocol Secure) is HTTP with encryption added, using SSL/TLS. Encryption scrambles the data so that anyone who intercepts it cannot read it.

A browser shows a padlock in the address bar when HTTPS is used. You should only type passwords or card numbers on HTTPS pages.

5.1 The internet and the World Wide Web · The explanation · step 3 of 25 · part 2 of 2

HTTP and HTTPS (continued)

?Why?

With plain HTTP, data travels as readable text. Someone on the same public Wi-Fi could read your password. HTTPS stops this.

!Watch out

HTTPS means the connection is encrypted. It does not prove the website is honest. A fake website can also use HTTPS.

5.1 The internet and the World Wide Web · The explanation · step 4 of 25 · part 1 of 2

What a web browser does

A web browser is application software that lets you find, fetch and view web pages. Examples are Chrome, Firefox, Safari and Edge.

Its main job is to render HTML: it reads the HTML code from the server and turns it into the page you see, with text, images and links.

Cambridge lists these other functions. Learn each one.

5.1 The internet and the World Wide Web · The explanation · step 4 of 25 · part 2 of 2

What a web browser does (continued)

Browser functionWhat it does
Renders HTMLTurns HTML code into a visible web page
Bookmarks / favouritesSaves the URL of a page so you can go back to it in one click
HistoryKeeps a list of pages you have visited, with dates and times
TabsLets you open several pages in one browser window
CookiesStores small files from websites on your device
Navigation toolsBack, forward, refresh/reload and home buttons; clickable hyperlinks
Address barWhere you type or see the URL; often also works as a search box

The explanation · 21 more steps

More on the lesson page

The lesson page has the rest of the explanation, step by step:

  • How a web page is retrieved, step by step
  • Cookies: session and persistent
  • What cookies are used for
  • Brute-force attack
  • Data interception
  • Distributed denial of service (DDoS)
  • Hacking
  • Malware: virus, worm and Trojan horse
  • Malware: spyware, adware and ransomware
  • Phishing and pharming
  • Social engineering
  • Solutions: access levels, anti-malware and authentication
  • Solutions: updates, checking messages and links
  • Solutions: firewalls and privacy settings
  • Solutions: proxy servers
  • Solutions: SSL
  • Matching threats to defences
  • Be precise, and amend with care
  • The 15-mark scenario question: plan first
  • Model answer in pseudocode and Python
  • How the 15 marks are awarded

Open the lesson page

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Quick quiz · 1 of 3

A proxy server…

  1. A Is the same as a router
  2. B Sits between users and the internet, filtering and caching
  3. C Stores the DNS

B. Sits between users and the internet, filtering and caching

It can block sites, hide the user's address and keep copies of popular pages.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Quick quiz · 2 of 3

The World Wide Web is…

  1. A Pages that use the internet via HTTP
  2. B The cables and routers
  3. C The same thing as the internet

A. Pages that use the internet via HTTP

The internet is the network. The web is one service on it.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Quick quiz · 3 of 3

DNS…

  1. A Stores cookies
  2. B Turns a domain name into an IP address
  3. C Encrypts the page

B. Turns a domain name into an IP address

The phone book of the internet.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Exit ticket

Answer on paper before you go. Then check.

  1. A session cookie…

    A Lasts for yearsB Is deleted when the browser closesC Is a type of virus

    B. Is deleted when the browser closes A persistent cookie stays. A session cookie goes with the session.

  2. Pharming is…

    A Being sent to a fake website even when you type the right addressB A fake email asking for a passwordC Guessing every password

    A. Being sent to a fake website even when you type the right address Phishing needs you to click. Pharming redirects you, often through poisoned DNS.

Year 11 · Computer Science · The internet and its uses · Lesson 5 of 5

Homework and the challenge

Homework

The CS 5 quiz; the How the Web Works 'Check yourself'.

End-of-unit challenge

End-of-unit test: past-paper questions on topic 5.