USB connections – the most common interface used globally to connect external devices to computers – are vulnerable to information ‘leakage’, making them even less secure than thought, a study has found. Researchers from University of Adelaide in Australia tested more than 50 different computers and external USB hubs and found that over 90 per cent of them leaked information to an external USB device. “USB-connected devices include keyboards, cardswipers and fingerprint readers which often send sensitive information to the computer,” said Yuval Yarom, research associate at 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,” said Yarom. “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,” he said. “That means keystrokes showing passwords or other private information can be easily stolen,” he added.
Yarom said that this ‘channel-to-channel crosstalk leakage’ is analogous with water leaking from pipes. “Electricity flows like water along pipes – and it can leak out,” Yarom said. “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,” he said. Researchers used a modified cheap novelty plug-in lamp with a USB connector to “read” every key stroke from the adjacent keyboard USB interface. The data was sent via Bluetooth to another computer. “The main take-home message is that people should not connect anything to USB unless they can fully trust it,” said Yarom.
“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,” he said. The long-term solution is that USB connections should be redesigned to make them more secure.