New Security Breach Reveals Risks of Eavesdropping via Laptop and Smart Speaker Microphones

The findings of the University of Florida and University of Electro-Communications’ study serve as a wake-up call in the digital age, emphasizing the need for ongoing research in the field of cybersecurity. With the rapid development of technology, especially in the context of artificial intelligence and machine learning, the landscape of threats to privacy continues to evolve, necessitating an equally dynamic response from researchers, developers, and policymakers alike.

Bioengineer.org

2 hours ago 

New Security Breach Reveals Risks of Eavesdropping via Laptop and Smart Speaker Microphones

by Bioengineer

June 11, 2025

in Technology

 

In closing, as technology continues to intertwine itself more deeply into the fabric of daily life, it becomes increasingly crucial for both consumers and manufacturers to prioritize the design of secure systems and devices. This study highlights an unsettling reality of modern technology—1 that while it provides endless benefits, it simultaneously opens doors to vulnerabilities, requiring an unwavering commitment to protect against unauthorized access and exploitation of sensitive information.

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Sound of Interference: Electromagnetic Eavesdropping Attack on Digital Microphones Using Pulse Density Modulation

 

Authors: 

Arifu Onishi, The University of Electro-Communications; S. Hrushikesh Bhupathiraju, Rishikesh Bhatt, and Sara Rampazzi, University of Florida; Takeshi Sugawara, The University of Electro-Communications

Abstract: 

We introduce a novel electromagnetic (EM) side-channel attack that allows for acoustic eavesdropping on electronic devices. 

This method specifically targets modern digital microelectromechanical systems (MEMS) microphones, which transmit captured audio via pulse-density modulation (PDM), that translate the analog sound signal into the density of output pulses in the digital domain. 

We discover that each harmonic of these digital pulses retains acoustic information, allowing the original audio to be retrieved through simple FM demodulation using standard radio receivers. 

An attacker can exploit this phenomenon to capture what the victim microphone hears remotely without installing malicious software or tampering with the device. We verify the vulnerability presence by conducting real-world evaluation on several PDM microphones and electronic devices, including laptops and smart speakers. 

• For example, we demonstrate that the attack achieves up to 94.2% accuracy in recognizing spoken digits, up to 2 meters from a victim laptop located behind a 25 cm concrete wall. 
• We also evaluate the attacker capability to eavesdrop on speech using popular speech-to-text APIs (e.g., OpenAI) not trained on EM traces, achieving a maximum of 14% transcription error rate in recovering the Harvard Sentences dataset. 
• We further demonstrate that similar accuracy can be achieved with a cheap and stealthy antenna made out of copper tape. 
• We finally discuss the limited effectiveness of current defenses such as resampling, and we propose a new hardware defense based on clock randomization.

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Sound of Interference: Electromagnetic Eavesdropping Attack on Digital Microphones Using Pulse Density Modulation

The term "Sound of Interference" refers to a recent research paper titled "

Sound of Interference: Electromagnetic Eavesdropping Attack on Digital Microphones Using Pulse Density Modulation". This paper highlights a vulnerability in digital microphones, specifically those using Pulse Density Modulation (PDM), which allows for remote eavesdropping via electromagnetic emissions. 

How the attack works: 

1. PDM Microphones: Modern digital microphones, especially MEMS (Micro-Electro-Mechanical Systems) microphones commonly found in laptops, phones, and smart speakers, use PDM to convert analog sound into a digital signal.
2. Electromagnetic Leakage: This conversion process generates electromagnetic radiation, which can be picked up by radio receivers.
3. Acoustic Information Retention: Crucially, each harmonic of the PDM signal retains acoustic information from the original sound.
4. FM Demodulation: Using simple FM demodulation with standard radio receivers, an attacker can extract and recover the audio information from these electromagnetic emissions. 

Key Findings: 

• Conversations can be intercepted up to 2 meters away, even through walls.
• The attack is accessible with inexpensive equipment, such as a copper tape antenna and an FM radio receiver, costing under $100.