Where did it go wrong?
A user cannot reach a shared drive. Is the cable loose? Is the address wrong? Is the program faulty? Is something blocking it?
Technicians solve this by working through layers, one at a time. Attackers think in layers too.
Today you place a security control at each one.
Key words
| Word | What it means |
|---|---|
| Network | Computers and devices linked so they can share data. |
| Layer | One level in a model, with its own job. |
| OSI model | A seven-layer model that describes how data moves across a network. |
| TCP/IP model | A four-layer model of the protocols the internet really uses. |
| Protocol | A set of rules for how devices talk to each other. |
| Packet | A small chunk of data sent across a network. |
| IP address | A number that identifies a device on a network. |
| VLAN | Virtual LAN: a group of switch ports that act as their own separate network. |
| Frame | A packet of data as it crosses one link, with its hardware addresses. |
| MAC address | The hardware address built into a network card. |
| Firewall | A gate that lets some traffic in or out and blocks the rest. |
| Encryption | Scrambling data so only a person with the right key can read it. |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can name the layers of the OSI and TCP/IP models, and match a security control to the layer where it works.
Starter: layouts
Have a go
Starter: layouts
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Cycle 1: the OSI model
The OSI model has seven layers. Each layer does one job and talks to the layers above and below.
From the top: 7 application, 6 presentation, 5 session, 4 transport, 3 network, 2 data link, 1 physical.
A memory aid, top to bottom: All People Seem To Need Data Processing. The environments series teaches what each layer does. Here you add the security view.
Worked example: one control per OSI layer
| Layer | Job in a few words | A security control |
|---|---|---|
| 7 Application | Programs such as web and email | Email filtering, safe sign-in, web application checks |
| 6 Presentation | Format and lock the data | Encryption such as TLS |
| 5 Session | Start and end a conversation | Time-outs and single logout |
| 4 Transport | Reliable delivery, ports | Firewall rules on ports |
| 3 Network | Addresses and routes | IP address rules, IPSec |
| 2 Data link | Frames over one link, MAC addresses | VLANs, port security on switches |
| 1 Physical | Cables and signals | Locked rooms, protected cabling |
The cells students fill in are left blank in this preview.
Check: OSI
Have a go
Check: OSI
4 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.