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Researcher: Cisco's Patch Against VoIP Hack Easily Bypassed

Earlier this month Ang Cui, a fifth-year graduate student from the Columbia University Intrusion Detection Systems Lab, demonstrated a series of vulnerabilities while presenting at the Amphion Forum. One of them, affecting VoIP offerings from Cisco, was previously patched, but the researcher claims that didn’t fix the issue.

Using a common Cisco-branded VoIP phone, Cui inserted and then removed a small external circuit board from the phone’s Ethernet port and starting using his own smartphone to capture every word spoken near the VoIP phone, even though it was still on-the-hook. Cisco said the vulnerability was patched in November, and was dismissive of the overall attack, as it required physical access to the device.

However, Cui countered that argument noting that the attack could be easily accomplished by a company visitor left unattended for a just few seconds. Further, in an interview with ThreatPost, he and his advisor, Salvatore J. Solfo, told Kaspersky Lab’s news service that the patch from Cisco was version specific, requiring only a slight modification made to the exploit in order to bypass November’s fix.

“The idea is that once you compromise the phone, to use the microphone to listen to what is going on in the room whether the phone is on the hook or not,” Cui told ThreatPost.

“Once you compromise the phone, you can use the phone as a general-purpose computer to attack other phones or devices on the network. It’s like a self-propagating worm that can attack a phone, printer, router, access points—all behind the firewall. The attacker has persistent presence on the network.”

In addition to the physical exploit, Solfo told ThreatPost that during an upcoming conference, Cui would demo the same attack remotely.

“The remote attack doesn’t require attacking standard network service protocols. We are using them only because of the opportunity provided by them to reach the phone. Cisco has to figure out how to prevent this from happening,” he said, stressing that the issue isn’t configuration related; it’s purely a Cisco development problem.

Cui’s research was carried out as part of a DARPA CRASH (from the I2O office) and IARPA Stonesoup Program, and he recently briefed agencies of the U.S. federal government about the potential for a serious attack on all its Cisco Unified VoIP phones.

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Steve Ragan is a security reporter and contributor for SecurityWeek. Prior to joining the journalism world in 2005, he spent 15 years as a freelance IT contractor focused on endpoint security and security training.