Networks & Cyber Safety

How computers talk

Every time you open a website, data races across the world and back in a fraction of a second. Let’s see how it travels, how it finds the right place, and how to stay safe out there.

Jump to the phishing game

1. What is a network?

A network is two or more computers connected so they can share data. Your home Wi-Fi is a small network. The internet is the biggest one of all: a network of networks, joining billions of devices around the world.

Key idea: a network just means devices connected to share data. The internet is simply networks joined to other networks.

2. Packets

Big things do not travel across a network in one piece. The data is chopped into small packets, each numbered and labelled with where it is going. They can take different routes, arrive out of order, and get put back together at the other end.

Why bother? If one little packet gets lost, only that one is resent, not the whole file. It is faster and more reliable.

3. Addresses & domains

Every device on a network has an IP address, a string of numbers like 142.250.70.196. Computers love numbers, but people do not. So we use domain names like google.com instead.

When you type a domain, the DNS (Domain Name System) looks it up and finds the matching IP address. Think of DNS as the internet’s phonebook: you know the name, it finds the number.

Check your understanding: What is a domain name like google.com for?

Exam practice · Year 9

In the URL https://www.bom.gov.au/weather/today, which part is the domain name? (1 mark)

Show the answer
  • www.bom.gov.au is the domain name (the address of the website).
  • https is the protocol, and /weather/today is the path to a particular page.

4. Hubs, switches & collisions

Inside a network, a device in the middle passes data between computers. There are two ways to do it, and the difference is the whole point:

  • A hub (the old way) copies every message to every computer. If two send at once, the signals collide and have to be resent.
  • A switch (the modern way) is smart: it sends each message only to the computer it is meant for. Far fewer collisions.
  • A router connects your whole network to other networks, including the internet.

A wants to message D. Try both:

A
B
C
D

A wants to send a message to D. Try each device and watch who receives it.

Hubs are basically extinct now (switches replaced them), but the idea explains data collisions, which is exactly why we moved to switches.

Check your understanding: A hub sends data to every computer. What problem can that cause?

5. HTTP & HTTPS

When your browser (the client) wants a web page, it sends a request to a server (the computer that stores the site). The server responds with the page. The language they use is HTTP: HyperText Transfer Protocol.

HTTPS is the same, but the S is for Secure: the data is encrypted so no one in between can read it. That is the little padlock in your address bar. If a site asks for a password and there is no padlock, be careful.

Exam practice · Year 9

What does HTTP stand for? (1 mark)

Show the answer
  • HyperText Transfer Protocol - the rules a browser and server use to send web pages.
  • HTTPS is the same thing but Secure (encrypted).

6. Where websites live

A website is just files (like the HTML you met in that module) sitting on a server that is always on, so anyone can request it. Putting your files on a server so the world can see them is called hosting.

You do not need to buy a server. You can host a site for free on services like GitHub Pages, Vercel, Netlify or Cloudflare Pages. Fun fact: this very site runs on GitHub Pages.

These services run in the cloud, which just means powerful computers in big data centres that you use over the internet instead of owning yourself. "The cloud" is really just someone else’s computer, somewhere, that you rent or use for free.

Check your understanding: What does it mean to "host" a website?

7. Cyber safety

Phishing is when a scammer pretends to be someone you trust to trick you into giving up a password, money or personal details. Watch for the red flags: a fake address, panic and urgency, a request for your password, or a deal that is too good to be true.

Tap Safe or Scam for each message, then see the red flags:

From: security@app1e-support.com

Your account is LOCKED. Verify your password in the next 24 hours or it will be deleted. Click here: bit.ly/ver1fy

From: prizes@free-iphone-now.net

CONGRATULATIONS! You have been chosen to win a free iPhone. Just enter your address and card details to claim your prize!

From: mr.h@school.vic.edu.au

Hi class, a reminder that your Python task is due Friday. No need to reply, just bring it to the lesson. See you then.

Module test

Five quick questions to check you have got it. Your best score shows on your My Progress page.

1. What is a network?

2. Data is broken into small numbered pieces to travel across a network. What are they called?

3. What does a domain name (like google.com) do?

4. What does the S in HTTPS give you?

5. An email says "You won! Click here and enter your password to claim." What should you do?

Class word cloud

We all use the internet every day. Add one thing you use it for.

Glossary

Network
Two or more computers connected to share data.
Internet
A worldwide network of networks.
Packet
A small numbered piece of data that travels across a network.
IP address
The numeric address of a device on a network.
Domain name
A human-friendly name (like google.com) that points to an IP address.
DNS
The Domain Name System: the internet’s phonebook, turning names into IP addresses.
Switch
Sends data only to the computer it is meant for (a hub sends to everyone).
Router
Connects a network to other networks, including the internet.
HTTP / HTTPS
The rules a browser and server use to send web pages. HTTPS is the secure (encrypted) version.
Hosting
Storing a website’s files on an always-on server so others can visit it.
Phishing
A scam that pretends to be someone you trust to steal passwords, money or data.
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