Friday, June 13, 2025

Eavesdropping on laptop, smart speaker microphones demonstrated in new security attack

University of Florida

Wall Demo — video:
A demonstration of the microphone attack through a 15 cm wall
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Credit: Sara Rampazzi

The ghostly woman’s voice pipes through the speakers, covered in radio static but her message intact from beyond — “The birch canoe slid on the smooth planks.”

A secret message from the other side? A spectral insight?

No, something much spookier: Voice recordings captured, secretly, from the radio frequencies emitted by ubiquitous, cheap microphones in laptops and smart speakers. These unintentional signals pass, ghost-like, through walls, only to be captured by simple radio components and translated back to static-filled — but easily intelligible — speech.

For the first time, researchers at the University of Florida and the University of Electro-Communications in Japan have revealed a security and privacy risk inherent in the design of these microphones, which emit radio signals as a kind of interference when processing audio data.

The attack could open up people to industry espionage or even government spying, all without any tampering of their devices. But the security researchers have also identified multiple ways to address the design flaw and shared their work with manufacturers for potential fixes going forward.

“With an FM radio receiver and a copper antenna, you can eavesdrop on these microphones. That’s how easy this can be,” said Sara Rampazzi, Ph.D., a professor of computer and information science and engineering at UF and co-author of the new study. “It costs maybe a hundred dollars, or even less.”

They used standardized recordings of random sentences to test the attack, giving the eerie impression of a ghostly woman talking about canoes or imploring you to “Glue the sheet to the dark blue background.” Each nonsense sentence instantly recognizable despite, in some cases, passing through concrete walls 10 inches thick.

The vulnerability is based on the design of digital MEMS microphones, which are widespread in devices like laptops and smart speakers. When processing audio data, they release weak radio signals that contain information about everything the microphone is picking up. Like other radio signals, these transmissions can pass through walls to be captured by simple antennas.

Even when someone is not intentionally using their microphone, it can be picking up and transmitting these signals. Common browser apps like Spotify, YouTube, Amazon Music and Google Drive enable the microphone sufficiently to leak out radio signals of anything said in the room.

The researchers tested a range of laptops, the Google Home smart speaker, and headsets used for video conferencing. Eavesdropping worked best on the laptops, in part because their microphones were attached to long wires that served as antennas amplifying the signal.

Rampazzi’s lab also used machine learning-driven programs from companies like Open AI and Microsoft to clean up the noisy radio signals and transcribe them to text, which demonstrated how easy it would be to then search eavesdropped conversations for keywords.

However, a series of fairly simple changes could greatly decrease the effectiveness of the attack. Changing where microphones are placed in laptops could avoid long cables, which amplify the radio leakage. Slight tweaks to the standard audio processing protocols would reduce the intelligibility of the signals.

The researchers have shared these ideas with laptop and smart speaker manufacturers, but it’s not clear if the companies will make the upgrades in future devices.

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

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

Researchers create new way to remove phosphorus from contaminated water

North Carolina State University

Researchers have created an inexpensive hydrogel that can filter phosphorus from contaminated surface waters, drinking water supplies or wastewater streams to reduce phosphorus pollution and reuse the phosphorus for agricultural and industrial applications. In addition to efficiently capturing and releasing phosphorus, the hydrogels can be reused multiple times – making them cost-effective.

Phosphorus is an essential element for many applications, particularly agricultural fertilizers. But there are two key challenges. First, the phosphorus used for farming and industrial applications primarily comes from mining operations, which rely on limited resources and can pose environmental problems. Second, high phosphorus levels in surface waters – from agricultural runoff, wastewater plants and other sources – contribute to significant water-quality problems such as eutrophication, leading to so-called “dead zones.”

“The idea of filtering phosphorus from contaminated waters is not new, but existing technologies rely on potent acids or bases to release the phosphorus once it has been captured,” says Jan Genzer, co-corresponding author of a paper on the work, and S. Frank and Doris Culberson Distinguished Professor of Chemical and Biomolecular Engineering at North Carolina State University. “Ultimately, this poses environmental challenges of its own and makes it expensive to harvest phosphorus using filtration technologies. We have made major strides toward solving this problem.”

The researchers created a hydrogel that combines two commercially available materials: polyethyleneimine (PEI), which is an inexpensive polymer whose molecular structure allows it to harvest phosphorus from water as the water passes through the material, and poly(methyl vinyl ether-co-maleic anhydride) (PMVEMA), which is an inexpensive polymer that bonds with the PEI to form a robust gel that allows water to pass through while maintaining its structural integrity.

In testing, the PEI/PMVEMA hydrogel was extremely efficient at removing phosphorus from contaminated water as it flowed through the material at room temperature. It also efficiently released the captured phosphorus at room temperature using mild bases.

“Our experiments suggest the hydrogel would be able to remove well over 90% of the phosphorus from wastewater or contaminated surface waters,” Genzer says. “We also demonstrated that we can reclaim up to 99% of that phosphorus for reuse. We also showed that the hydrogel can then be reused with minimal decline in performance. For example, after being used three times, we could still reuse 97.5% of the phosphorus.

“To put this in context, current phosphorus filtration materials cost $20-300 per pound of phosphorus they can capture,” says Genzer. “Our material costs $23 per pound of phosphorus removed if you only use it once. But you can use it over and over again. If you use the hydrogel twice, the cost drops to $8 per pound of phosphorus harvested. If you use it 50 times, the price drops to less than 50 cents per pound.

“We have filed a provisional patent for the material and are looking for industry partners interested in incorporating the material into practical applications for wastewater treatment, environmental remediation, and harvesting phosphorus for agricultural and industrial use,” says Genzer.

“From a research standpoint, the next big challenge is determining how to use this material to harvest phosphorus from contaminated soils. That is a more complex problem than removing phosphorus from liquids.”

The paper, “Functional Hydrogels for Selective Phosphate Removal from Water and Release on Demand,” is published in Langmuir. The paper’s first author is Jiangfeng Xu, a Ph.D. student at NC State. The paper’s co-corresponding author is Kirill Efimenko, a research associate professor of chemical and biomolecular engineering at NC State. The paper was co-authored by Christopher Gorman, a professor of chemistry at NC State; Yaroslava Yingling, Kobe Steel Distinguished Professor of Materials Science and Engineering at NC State; and Lisa Castellano, a research associate at NC State.

This work was supported by the Science and Technologies for Phosphorus Sustainability (STEPS) Center, a National Science Foundation Science and Technology Center based at NC State that is funded under grant CBET-2019435.

Journal

Langmuir

DOI

10.1021/acs.langmuir.5c00679