RTL-SDR is low-cost software-defined radio hardware built around repurposed digital TV receiver chips. Instead of using dedicated radio circuitry for every task, it delivers raw I/Q samples to software, which then demodulates, analyzes, or visualizes the signal. That makes it a popular entry point for radio experimentation because a cheap USB device and the right software can cover a wide range of frequencies and signal types.
In cyber security, RTL-SDR matters because many wireless systems are part of the attack surface. Defenders use it to inspect RF environments, detect rogue transmitters, study device behavior, and test how much information leaks over the air. Researchers and attackers can also use it to capture and analyze unencrypted or weakly protected signals, making it a practical tool for both offense and defense. Its value is flexibility: one device can support reconnaissance, troubleshooting, and protocol analysis.