← ACARA Digital Technologies Years 9–10

Network (hardware) firewall

A device or router feature between a local network and the internet that filters inbound and outbound traffic for every device behind it, not just one.

Part of: ACARA Digital Technologies Years 9–10 — Networked Systems and Access Control — Module 123, WA Computer Science ATAR Year 11 — Network Communications — Module 113, WA Computer Science ATAR Year 11 — Cyber Security — Module 117

Understanding Network (hardware) firewall in ACARA Digital Technologies Years 9–10

What it does: The diagram shows the firewall in the path between the internet and the LAN, so all traffic must pass through it. A single rule at the network edge applies to every device behind the firewall, and it filters traffic leaving the network as well as entering it. It checks data coming in from the internet and data going out from devices on the network.

Common mistakes: A network firewall sits between the local network (LAN) and the internet (WAN). It is not placed inside one laptop. It should be firewall = between(LAN, WAN). The comment says inbound Telnet (port 23) should be blocked, so the rule must deny it. It should be rule 2: deny in port 23.

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This module's key terms are also in a printable crossword (Modules 116–154) and word search (Modules 116–225).

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Learning

Duo

Where does a network (hardware) firewall sit?

Inside one laptop's apps folderBetween the local network and the internet

Matches

A network firewall only protects the one laptop it is installed on.

↓

This describes software on a single device. A network firewall sits between the local network and the internet and filters traffic for every device behind it.

Applying

Meanings

Term

network firewall

Meaning

A device or router feature between a local network and the internet that filters inbound and outbound traffic for every device behind it, not just one.

Practice

FIREWALL at router between LAN and internet

Testing

Gaps

Internet -> -> Switch -> PCs

Check Answer

Spots

1firewall = inside(laptop)

2for each device in LAN:

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Quick Questions

1. Where does a network (hardware) firewall sit?

A. Between the local network and the internet ✓

B. Inside one laptop's apps folder

A network firewall sits at the edge of the local network, so traffic must pass through it to get in or out.

2. Which firewall protects many devices at once?

A. A network firewall at the router ✓

B. A firewall app on one phone

A network firewall filters traffic for every device behind it. Software on one device only protects that device.

3. Which of these can act as a network firewall?

A. A USB drive plugged into one computer

B. A home router with its firewall feature turned on ✓

A network firewall can be a router feature or a dedicated appliance placed at the edge of the network.

4. A network firewall filters which traffic?

A. Both inbound and outbound traffic ✓

B. Only traffic that stays inside the LAN

It checks data coming in from the internet and data going out from devices on the network.

5. A new tablet joins your home Wi-Fi. What happens with the router's firewall?

A. The tablet is unprotected until it has its own firewall

B. The tablet is protected without installing anything ✓

Every device behind the network firewall has its traffic filtered, including new devices.

Match the Pairs

network firewall → A device or router feature between the local network and the internet that filters traffic for every device behind it

inbound traffic → Data coming from the internet into the local network, which the firewall checks before letting it reach a device

A network firewall can run on a router or a dedicated appliance placed between the LAN and the internet → Internet -> Firewall -> Switch -> Devices

One rule on a network firewall protects many devices at once, including outbound traffic → DENY outbound port 23 for all devices

A network firewall only protects the one laptop it is installed on. → This describes software on a single device. A network firewall sits between the local network and the internet and filters traffic for every device behind it.

Layout: Laptop -> Switch -> Internet -> Firewall → The firewall is placed after the internet, so traffic reaches the network without being filtered. It must sit between the local network and the internet.

Key Term

network firewall

A device or router feature between a local network and the internet that filters inbound and outbound traffic for every device behind it, not just one.

Fill in the Blanks

1. Internet -> Firewall -> Switch -> PCs

Hint: Type the device that sits between the internet and the local network and filters the traffic.

2. RULE 1: ALLOW outbound TCP port 443

Hint: Type the direction word for traffic leaving the local network for the internet.

3. RULE 2: DENY inbound TCP port 23

Hint: Type the action keyword that blocks matching traffic instead of letting it through.

4. FOR EACH device IN LAN firewall.check(device.traffic) END FOR

Hint: Type the device that checks the traffic of every device on the local network.

5. Software firewall: protects 1 device Network firewall: protects all devices

Hint: Type the word that says how many devices behind the network firewall are protected.

Spot the Error

Question 1

A firewall = inside(laptop)

B for each device in LAN:

C filter(device.traffic)

Line A — A network firewall sits between the local network (LAN) and the internet (WAN). It is not placed inside one laptop. It should be firewall = between(LAN, WAN).

Question 2

A # block inbound Telnet

B rule 1: allow out port 443

C rule 2: allow in port 23

Line C — The comment says inbound Telnet (port 23) should be blocked, so the rule must deny it. It should be rule 2: deny in port 23.

Question 3

A firewall = laptop.firewall

B devices = [laptop, phone, TV]

C protected = devices

Line A — A network firewall runs on the router or an appliance so it protects every device behind it. A firewall on the laptop would protect only the laptop. It should be firewall = router.firewall.

Question 4

A direction = 'inbound'

B source = 'LAN'

C destination = 'LAN'

D fw.check(source, destination)

Line B — Inbound traffic comes from the internet and goes into the LAN. The source should be 'internet', not 'LAN'.

Question 5

A packet.src = '192.168.1.5'

B packet.dst = '8.8.8.8'

C direction = 'inbound'

D fw.check(packet, direction)

Line C — The packet starts at a private LAN address and is going to an internet address, so it is leaving the network. The direction should be 'outbound'.

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