BLACK HAT EUROPE – London – An inexpensive Android hacking tool can create a covert communications channel in the power current generated while a smartphone charges on a power bank.
The so-called "PowerSnitch" attack, which was demonstrated here this week by Oxford University researcher Riccardo Spolaor, shows that a determined hacker doesn't actually need a network connection to hack a targeted smartphone and steal stored data such as passwords. Public power banks, and even private power bank devices, are vulnerable to the attack – which works even when the phone is equipped with a data-blocker device for protecting the data pin in the phone's power port.
PowerSnitch consists of both the app and a £17 (US $23.64) decoder device that translates the power signal via GNURadio to the data it siphons. The portable decoder is a stealthier version of a large prototype Spolaor and his fellow researchers – Laila Abudahi and professor Radha Poovendran of the University of Washington, professor Ivan Martinovic of Oxford, and Elia Dal Santo of the University of Padua in Italy – built in 2017 to hack into Android via the power charge.
"We used a big device [then]," Spolaor said. "So this time we wanted to see something less powerful and cheaper and even [more] deployable everywhere."
PowerSnitch is a targeted attack that requires the attacker to either lure the victim into downloading the malicious app (disguised as a legitimate one, such as an alarm clock) or to manually load the app on the victim's smartphone. "Everything depends on the attacker," Spolaor said. "He has to know his target in advance" and get the PowerSnitch onto the victim's Android somehow. Then he can exfiltrate data via power consumption. He could look at the phone's memory for stored passwords, contact lists, and photos, for example.
The decoder is slipped into the power bank, he said, and can be deployed in a power-port socket. The device consists of a sensor, Wi-Fi module, micro SD card, and SPI card reader.
The data exfiltration rate is low, at around 2 bits per second, he said, due to the power burst delay in the charging process. PowerSnitch, in effect, "turns the smartphone into a telegraph" that grabs the binary information from the current, he said.
"It's using only the surplus current, so it doesn't affect the battery recharging," he said.
Protecting an Android phone from such an attack via tampered power banks is really simple: Just power off the phone when charging it.
The researchers also plan to study whether the Apple iPhone is susceptible to the attack.
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