Learn how networks defend themselves by checking traffic, blocking unsafe requests and using proxy servers as a safer middle point between users and the internet.
When a computer connects to the internet, data travels in and out of the network.
Some traffic is safe. Some traffic may be unwanted, suspicious or harmful. A network needs a way to check what should be allowed through.
A firewall can be hardware, software, or both.
It examines incoming and outgoing network traffic and checks whether it matches the rules or criteria that have been set.
A security guard checks people before they enter a building.
If someone is on the approved list, they can enter. If they are banned or suspicious, they are refused entry.
A firewall works in a similar way for network traffic.
A firewall can use criteria such as allowed websites, blocked IP addresses, or closed ports.
Traffic that meets the criteria is allowed through. Traffic that does not meet the criteria is blocked or rejected.
| Firewall action | What it means |
|---|---|
| Allow | Traffic meets the rules |
| Block | Traffic does not meet the rules |
| Close a port | Stops traffic using that route |
A proxy server acts as an intermediary. This means the user does not connect directly to the web server.
The request goes to the proxy server first. The proxy can then pass the request on, block it, or respond using stored data.
In an office, visitors do not go directly to every worker. They go to reception first.
The receptionist can pass on requests, answer common questions, hide private office details, and stop unwanted visitors.
A proxy server does a similar job for network requests.
Two important proxy server functions are often tested.
A proxy can hide the public IP address of the user or network. It can also use caching, which means storing copies of frequently requested web pages.
| Proxy feature | How it helps |
|---|---|
| Hide IP address | Makes the user/network less directly exposed |
| Caching | Returns stored pages more quickly and reduces requests |
| Block requests | Stops access to unsuitable or unsafe content |
A firewall focuses on checking traffic against rules and blocking or allowing it.
A proxy server sits between the user and the internet. It can hide IP addresses and store cached copies of web pages.
| Firewall | Proxy Server |
|---|---|
| Checks traffic against criteria | Acts as an intermediary |
| Allows or blocks traffic | Can hide public IP address |
| Can block ports | Can cache web pages |
Exam answers need more than "it blocks hackers". Explain how the firewall makes its decision.
Describe how a firewall can help protect a network.
Students often give firewall answers when asked about proxy servers.
For proxy servers, remember the features that make them distinct: they can hide the public IP address and cache frequently requested web pages.
That answer is too vague because it does not explain what the firewall actually does.
A firewall protects a network by examining traffic and allowing or blocking it based on set rules.
A proxy server acts as an intermediary between the user and the internet. It can hide the public IP address and cache frequently requested pages.
The best exam answers explain what the protection does, not just the name of the tool.
You have now completed the Knowledge Library staircase for Internet & Security. The Learning Hub will help you practise these ideas with interactive examples and exam-style questions.