Cell phones and other handheld devices could become a great way to listen in on spoken conversations, researchers at George Mason University said this week.

In a paper (PDF), researchers Ryan Farley and Xinyuan Wang describe several new plays on the concept of "microphone hijacking," which has been used for years. The idea is to put spyware on mobile devices -- including laptops, cell phones, and PDAs -- that can use their built-in microphones to eavesdrop on nearby conversations.

In the past, this eavesdropping has usually been done via the victim's own cell phone or other device. But Farley and Wang describe a way to bug nearby devices belonging to nearby users to achieve similar results.

Under the researchers' concept, called a "roving bugnet," the eavesdropper would use a piece of malware called a "bugbot" to listen in on in-person interactions via a nearby smartphone or laptop. Such attacks would be more likely to target specific people (such as an executive or a spouse) than as a broad attack, the researchers say.

Farley and Wang conducted experiments on Windows XP and Mac OS laptops. The researchers directed their bugbot to join an Internet Relay Chat channel so they could remotely enable and disable each laptop's microphone, streaming real-time conversations nearby. The same thing, they said, could be done on almost any smartphone.

"Remote surveillance is a significantly invasive threat, arguably even more so than identity theft," the paper says. "As it stands now, most vulnerable devices do not have the protection necessary to distinctly address microphone or camera hijacks. As a growing number of mobile devices with exploitable operating systems gain more reliable Internet access, this longstanding problem is reaching a critical potential."

The paper also describes methods for detecting and mitigating remote surveillance attacks, including the use of a convincing, recorded audio loop that could help keep the attacker online longer in order to help track him down.

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