DeHiREC: Detecting Hidden Voice Recorders via ADC Electromagnetic Radiation

Unauthorized covert voice recording brings a remarkable threat to privacy-sensitive scenarios, such as confidential meetings and private conversations. Due to the miniaturization and disguise characteristics, hidden voice recorders are difficult to be noticed in their surroundings. In this paper, we present DeHiREC, the first proof-of-concept system that can detect offline hidden voice recorders from their electromagnetic radiations (EMR). We first characterize the unique patterns of the emanated EMR signals and then locate the EMR source, i.e., the analog-to-digital converter (ADC) module embedded in the mixed signal system-on-chips (MSoCs). Since these unintentional EMR signals can be extremely noisy and weak, accurately detecting them can be challenging. To address this challenge, we first design an EMR Catalyzing method to stimulate the EMR signals actively and then employ an adaptive-folding algorithm to improve the signal-to-noise ratio (SNR) of the sensed EMRs. Once the sensed EMR variation corresponds to our active stimulation, we can determine that there exists a hidden voice recorder. We evaluate the performance of DeHiREC on 13 commercial voice recorders under various impacts, including interference from other devices. Experimental results reveal that DeHiREC is effective in detecting all 13 voice recorders and achieves an overall success rate of 92.17% and a recall rate of 86.14% at a distance of 0.2 m.