Keep the warehouse off guest Wi-Fi
A firm keeps its customer data in a warehouse server. The firm also gives visitors Wi-Fi. If both sit on one flat network, a visitor's phone is a few steps from the customer data.
A good network (computers joined together) has a guard at the gate, separate zones inside and someone watching. Today you learn the rules for the guard, keeping networks apart and watching traffic.
Key words
| Word | What it means |
|---|---|
| Firewall | A guard that decides which network traffic may pass. |
| Rule | One instruction in a firewall: allow or deny this traffic. |
| Inbound | Traffic coming into a network. |
| Outbound | Traffic leaving a network. |
| Port | A numbered door on a computer for one kind of traffic. |
| IP address | The number that names a computer on a network. |
| Segregation | Keeping parts of a network apart. |
| VLAN | Virtual LAN: one physical network split by software into separate groups. |
| Monitoring | Watching traffic and logs all the time to spot problems. |
| Network | Computers joined together so they can share data. |
| Database | An organised store of data that programs can search. |
| Protocol | A set of rules for how computers talk. |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can describe how a firewall is set up, how networks are kept apart and how traffic is watched.
Starter: what you already know
Have a go
Starter: what you already know
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
A firewall checks traffic against rules
A firewall checks traffic against a list of rules. Each rule says allow or deny.
Direction: an inbound rule is for traffic coming in. An outbound rule is for traffic going out. You may block both.
Good practice: deny everything, then allow only what is needed. The first rule that matches decides.
Four ways to write a rule
Traffic type rules: by kind of traffic, such as web, email or file transfer (a protocol).
Application rules: by the program, for example allow a video call app but block a file sharing app.
IP address rules: by where traffic comes from or goes to. Block a bad address. Allow only the office.
Port rules: by port number, such as allow 443 and deny 23.
Worked example: a firewall list
| Order | Direction | Port | Action | Why |
|---|---|---|---|---|
| 1 | In | 443 | Allow | Staff report pages must be reachable |
| 2 | In | 22 | Allow, only from the office address | Admin login, limited by IP address |
| 3 | In | 5432 | Deny | The database is for the reporting server only |
| 4 | Out | 25 | Deny, except the mail server | Stops infected computers sending spam |
| 5 | Any | Any | Deny | Everything else is blocked |
The cells students fill in are left blank in this preview.
Check: firewall rules
Have a go
Check: firewall rules
4 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.