Hackers can hear through walls using radio waves

The laptop’s microphone is broadcasting everything it hears because the radio waves can pass through concrete walls and are captured by anyone with any basic equipment for under $100.

Security researchers found that modern digital microphones in laptops and smart speakers accidentally leaked audio as electromagnetic signals, creating a new form of wireless eavesdropping that requires no hacking, no malware, and no physical access to the device. Vulnerability can affect millions of devices around the world and can be exposed to private conversations that are corporate espionage or government surveillance.

The attack works because of how the digital microphone handles sound. These tiny components, called MEMS microphones, convert audio into digital pulses containing original speech residues. These pulses produce weak radio emissions, which leak out from devices such as invisible broadcasts.

“With the FM radio receiver and copper antenna, you can eavesdrop on these microphones,” said Sara Rampazzi, a professor of computer and information science and engineering at the University of Florida. “It costs a hundred dollars, or less.”

Through concrete ghost voices

The researchers proved their point using a creepy demonstration. A woman’s voice is static but understandably twisted, appearing from radio devices such as “a birch canoe sliding on smooth boards” and “glue the sheets on a dark blue background”. Each transmission passes through concrete walls up to 10 inches thick.

The team tested laptops, Google Home Smart speakers, and video conferencing headphones. Laptops proved to be the most vulnerable because their microphones are connected through long internal wires like antennas, thus amplifying leaked signals.

What made this attack particularly concerned? Your microphone does not need to be actively recorded. Just open up common apps (Spotify, YouTube, Amazon Music, or Google Drive) to make the microphone enough to leak radio signals from nearby conversations.

AI makes things worse

The researchers have not stopped proving that they can capture garbled audio. They sent radioactively entangled recordings into commercial voice-to-text software from companies such as OpenAI and Microsoft. The AI ​​system successfully cleaned up the static and converted the eavesdropped conversation into searchable text.

In controlled tests, the attack reached 94.2% accuracy even if the target laptop sat behind a 25-centimeter concrete wall. For longer sentences, the system has a transcriptional error rate of only 14%, which is enough to understand most conversations.

These implications go far beyond privacy issues. Industrial espionage is possible without having to touch competitors’ equipment. Government surveillance is invisible, and only a truck parked outside the building is required. Corporate meetings allegedly held in safe rooms can be monitored in the parking lot.

Technical breakthrough

What was not emphasized in the initial report was that the researchers found that multiple harmonics of the digital pulse retained the acoustic information. This discovery reveals why the attack works so effectively – it is not only a frequency leaking audio, but it can also combine several frequency bands to reconstruct speech with amazing clarity.

The vulnerability stems from pulse density modulation, which microphones are used to convert analog sound waves into digital data. Each pulse contains traces of the original audio, and as these pulses propagate every second, they create a radio fingerprint of everything the microphone hears.

The main findings of the study include:

• Attack works through concrete walls up to 25 cm thick
• Simple copper strap antenna proves to be as effective as professional equipment
• No software installation or device tampering is required
• Commercial AI greatly improves transcriptional accuracy
• The multiple device types affected, laptops are the most vulnerable

Solution

The researchers identified some potential repairs. Removing the microphone away from the long cable running inside the laptop can reduce signal amplification. Adjusting the audio processing protocol may cause leaked information to exceed useful recovery.

More complex defenses involve randomizing the time of digital pulses, which makes it nearly impossible for an attacker to extract coherent audio from radio emissions. Think of it as adding white noise directly to the electromagnetic characteristics.

The team has shared these defensive strategies with equipment manufacturers, although it is not clear whether the company will implement changes in future products. Until then, invisible radio chats with millions of microphones continued to broadcast our private moments to anyone at the right frequency.

Currently, users have limited options besides realizing that their devices may have more options than they realize. Assuming that our private conversations remain private the age may end, once with radio waves.

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