Networking III – SS3 Digital Technologies Lesson Note (Second Term)

Network security is the set of tools and habits used to protect files, devices and networks from hackers. It rests on three aims: confidentiality, integrity and availability. Firewalls filter data, VPNs and encryption hide data from watchers, and good habits such as strong passwords, updates and multi-factor authentication reduce the risk of attack.

Behavioural objectives

By the end of the lesson, students should be able to:

• explain what network security is and state the three parts of the C-I-A triad;
• describe how a firewall protects a network;
• explain what a VPN does on a public network;
• distinguish plaintext from ciphertext and explain encryption;
• identify phishing and malware and list ways to stay safe online.

What is network security?

In the real world, you lock your front door to keep thieves out. In the digital world, network security is the set of locks, fences and guards we use to protect our files and devices from “cyber-thieves” (hackers).

Without security, anyone on the internet could peek into your computer, steal your bank details or delete your school assignments.

What is the C-I-A triad?

The three pillars of security are:

1. Confidentiality: Only the right people should see the data.
2. Integrity: The data should not be changed or tampered with by anyone else.
3. Availability: The network should be working whenever the owner needs it.

What is a firewall?

A firewall is the most basic piece of security. Imagine a security guard standing at the gate of a compound. Every person who wants to enter must show their ID. If they are not on the list, the guard turns them away.

On your computer, the firewall looks at every “packet” of data trying to enter or leave your network.

• It checks where the data is coming from.
• It checks what kind of data it is.
• If the data looks suspicious or comes from a “bad neighbourhood” on the internet, the firewall blocks it instantly.

What is a VPN?

Using the public internet is like walking down a busy street. Everyone can see where you are going and what you are carrying. If you use the Wi-Fi at a coffee shop or an airport, a hacker nearby might be able to “sniff” your data.

A VPN (Virtual Private Network) creates a secret tunnel for your data. Even though you are using the public internet, your data is hidden inside this tunnel.

• To anyone watching, your data looks like scrambled gibberish.
• Your real location (IP address) is hidden, so it looks like you are browsing from a different place entirely.

What is encryption?

A VPN makes your data look like gibberish by using encryption. Encryption is the process of turning a readable message into a secret code. You can only read the message if you have the “key”.

• Plaintext: “My password is 123” (easy for hackers to read).
• Ciphertext: “Xy$8@!qP9” (what a hacker sees after encryption).

When you use a secure network, your computer “locks” the data with a key before sending it. The website at the other end has the matching key to “unlock” it. Even if a thief steals the message in the middle, they cannot understand it.

What are the common threats and how can you stay safe?

Even with firewalls and VPNs, hackers try to trick people, because humans are often the weakest link.

Threats to watch out for

1. Phishing: Fake emails that look like they are from your bank or school, asking you to click a link and “update your password”.
2. Malware: “Bad software” that hides inside free games or movies you download from untrusted sites.

Your security checklist

• Use strong passwords: Do not use “1234” or your birthday. Use a mix of letters, numbers and symbols.
• Update your software: The “Update Windows” pop-ups that seem annoying are fixing security holes. Install them.
• Enable MFA (Multi-Factor Authentication): Your phone asks “Is this really you?” after you type your password. It is one of the best ways to stop hackers.

Evaluation

1. What is network security?
2. State the three parts of the C-I-A triad and explain each one.
3. Explain how a firewall protects a network.
4. What is the difference between plaintext and ciphertext?
5. Why is it risky to use public Wi-Fi without a VPN?

Assignment

1. In your own words, explain what phishing and malware are, and give one way to protect yourself from each.
2. Write down the three items on the security checklist and say why each one helps.