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USB Connections Make Snooping Easy

More than 90% of USB connections are vulnerable to information “leakage”, making them even less secure than has been thought, according to research presented at the USENIX Security Symposium in Vancouver in August.

“USB-connected devices include keyboards, card-swipers and fingerprint readers, which often send sensitive information to the computer,” says project leader Dr Yuval Yarom of The University of Adelaide. “It has been thought that because that information is only sent along the direct communication path to the computer, it is protected from potentially compromised devices.

“But our research showed that if a malicious device or one that’s been tampered with is plugged into adjacent ports on the same external or internal USB hub, this sensitive information can be captured. That means keystrokes showing passwords or other private information can be easily stolen.

“Electricity flows like water along pipes, and it can leak out,” Yarom says. “In our project, we showed that voltage fluctuations of the USB port’s data lines can be monitored from the adjacent ports on the USB hub.”

Yarom says other research has shown that if USB sticks are dropped on the ground, 75% of them are picked up and plugged into a computer. But they could have been tampered with to send a message via Bluetooth or SMS to a computer anywhere in the world.

“The main take-home message is that people should not connect anything to USB unless they can fully trust it,” Yarom says. “For users it usually means not to connect to other people devices. For organisations that require more security, the whole supply chain should be validated to ensure that the devices are secure.”

Yarom says the long-term solution is that USB connections should be redesigned to make them more secure. “The USB has been designed under the assumption that everything connected is under the control of the user and that everything is trusted, but we know that’s not the case. The USB will never be secure unless the data is encrypted before it is sent.”