The building blocks of an IoT system
In short: An IoT system has five building blocks: the device, the connectivity that carries its data, the platform that receives and stores it, the application that makes sense of it, and the user who acts on it. A weakness in any one block can undermine the whole system.
Seeing the whole system
When people say "IoT device" they often mean only the gadget on the wall. In practice that gadget is just one part of a chain. Data has to travel from the device, through a network, to a platform, into an application and finally to a person or another system that makes a decision. Thinking in building blocks helps you design, troubleshoot and secure the whole chain.
The five blocks
| Block | Job | Example | Security concern |
|---|---|---|---|
| Device | Sense or act on the physical world | Temperature probe, smart lock | Default passwords, old firmware, physical tampering |
| Connectivity | Carry data to and from the device | Wi-Fi, Bluetooth Low Energy, LoRaWAN, 4G, a gateway | Eavesdropping, spoofing, weak radio encryption |
| Platform | Register devices, receive messages, store data | A cloud IoT hub or a self-hosted broker | Weak device authentication, exposed APIs |
| Application | Turn data into insight and decisions | Energy dashboard, rules that send alerts | Injection flaws, broken access control |
| User | View, configure and respond | Mobile app, operator console | Phishing, shared accounts, no multi-factor authentication (MFA) |
Inside the device
Most devices are built around a microcontroller unit (MCU), a small chip that contains a processor, memory and input/output pins. It runs firmware, the software stored permanently on the device. Sensors feed it readings; actuators such as relays, motors or valves let it change something. A radio module (sometimes built into the MCU) handles communication, and a power source keeps everything running. Better designs add a secure element or trusted platform module to protect cryptographic keys from being read out.
Gateways and the cloud
Many small devices cannot speak to the internet directly. A gateway sits nearby, collects their data over a short-range or low-power radio, translates protocols and forwards the results over Internet Protocol (IP). The gateway is also a useful security checkpoint, because it can filter traffic and hold credentials that tiny sensors cannot.
The platform is often a cloud service, but it can equally be a server in your own building. Either way it should keep a device registry so that only known, authenticated devices can send data.
Tip: in exams and design reviews, walk through the blocks in order and ask "what could go wrong here, and who owns it?" This simple habit uncovers most gaps.
Practice
Which building block would a smart-home hub that links Zigbee sensors to Wi-Fi belong to?
What is firmware?
Why should the platform keep a device registry?
Key takeaways
- IoT is a chain: device, connectivity, platform, application and user.
- A device combines an MCU, sensors, actuators, a radio, power and ideally secure key storage.
- Gateways bridge constrained devices to IP networks and act as checkpoints.
- The platform should authenticate devices against a registry.
- Security has to cover every block, not just the gadget.
Original content written by Mohamed Fayas for FM TecHub. © 2026 FM TecHub. You're welcome to share a link to this page; please don't copy the text elsewhere without permission.