According to a team of researchers at the Ben-Gurion University of the Negev, this technique can give hackers complete control over the device.
“Phone touchscreens, and other similar hardware components such as orientation sensors, wireless charging controllers, and NFC readers, are often produced by third-party manufacturers and not by the phone vendors themselves. Third-party driver source code to support these components is integrated into the vendor’s source code. In contrast to “pluggable” drivers, such as USB or network drivers, the component driver’s source code implicitly assumes that the component hardware is authentic and trustworthy. As a result of this trust, very few integrity checks are performed on the communications between the component and the device’s main processor” reads the research paper.
The researchers used for their experiments two Android devices, a Huawei Nexus 6P smartphone which uses a touchscreen controller from Synaptics, and an LG G Pad 7.0 tablet with an Atmel controller.
The experts separate the touchscreen controller from the main assembly board and access the copper pads, they made this operation by using a hot air blower.
They connected the pads to an integrated chip that was used to launch a chip-in-the-middle attack and to manipulate the communication bus.
“We construct two standalone attacks, based on malicious touchscreen hardware, that function as building blocks toward a full attack: a series of touch injection attacks that allow the touchscreen to impersonate the user and exfiltrate data, and a buffer overflow attack that lets the attacker execute
privileged operations. Combining the two building blocks, we present and evaluate a series of end-to-end attacks that can severely compromise a stock Android phone with standard firmware.” continues the paper”
The researchers focused their experiments on components with a limited hardware interface, they assumed that the technician that replaced the screen is not involved and does not conduct any operations other than replacing the broken component with a malicious one that has been provided to them.
The experts leveraged on cheap STM32L432 and Arduino microcontrollers, which go for $10 each, in the experiments.
The malicious exploit vulnerabilities in the device driver to compromise the mobile devices without impacting its operations making impossible to discover the hack.
The experts shared a video PoC of the hack in which they show how to use a malicious touch screen to install arbitrary software and take complete control of the targeted device. The attacker can take pictures with the camera and transfer them via email, replace a legitimate URL with a phishing URL, capture and exfiltrate screen unlock patterns.
The researchers were able to completely hijack a phone roughly in 65 seconds, other malicious actions such as replacing a URL are instantaneous.
In February, the experts notified Google of the vulnerabilities in Synaptics device driver, the issues were addressed in June and fixed in the June 2017 Android security updates. The experts are also notifying the flaws to developers of the Armel device driver.
“The threat of a malicious peripheral existing inside consumer electronics should not be taken lightly. As this paper shows, attacks by malicious peripherals are feasible, scalable, and invisible to most detection techniques. A well motivated adversary may be fully capable of mounting such attacks in a large scale or against specific targets. System designers should consider replacement components to be outside the phone’s trust boundary, and design their defenses accordingly.” concluded the researchers that also included a series of hardware-based countermeasures to prevent the attacks they analyzed.
Researchers speculate other mobile devices are also vulnerable to these types of attacks.
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(Security Affairs – touchscreen replacement, chip-in-the-middle attack )