A sensor node is a device that collects information from its environment and then processes, stores, or forwards that data. It may be a tiny embedded system, an IoT gadget, or a small computer with sensors such as microphones, cameras, motion detectors, or temperature probes. In many designs, the node does some local analysis first and only sends selected results onward.
Sensor nodes matter in cyber security because they extend the attack surface into the physical world. If an attacker can access the device, they may steal raw data, alter readings, disable alerts, or use the node as a foothold into the rest of the network. Defenders reduce risk by limiting permissions, encrypting traffic, updating firmware, and deciding what data should stay local. In practice, a harmless project can become a sensor node the moment it starts observing its surroundings.