The FBI is warning actors in the private sector about a rapid diffusion of stealthy keystroke loggers disguised as USB phone chargers.
“KeySweeper is a covert device that resembles a functional Universal Serial Bus (USB) enabled device charger which conceals hardware capable of harvesting keystrokes from certain wireless keyboards” reads the FBI’s alert.” If placed strategically in an office or other location where individuals might use wireless devices, a malicious cyber actor could potentially harvest personally identifiable information, intellectual property, trade secrets, passwords, or other sensitive information. Since the data is intercepted prior to reaching the CPU, security managers may not have insight into how sensitive information is being stolen.”
Samy Kamkar designed a cheap USB wall charger that can eavesdrop on almost any Microsoft wireless keyboard, KeySweeper is a stealthy Arduino-based device that works like a generic USB mobile charger, but he has the capability to sniff, decrypts and send back keystrokes from a Microsoft wireless keyboard in the vicinity. KeySweeper can send captured data back to the operator over the Internet or using an optional GSM chip.
“KeySweeper is a stealthy Ardunio-based device camouflaged as a wall charger that wirelessly sniffs, decrypts, logs and reports-back all keystrokes from any Microsoft wireless keyboard in the vicinity,” explained Kamkar.
Kamkar has also detailed the steps to build the KeySweeper USB wall charger explaining that it is easy and cheap to assemble the spying device, the unit cost ranges from $10 to $80 depending on functions included. The instructions on how to build the device are available online on GitHub.
The KeySweeper also includes a web-based tool for live keystroke monitoring, it could be used by an attacker to send back SMS alerts triggered by specific typed keystrokes, like usernames or URLs. While the device is logging the keystrokes he is able to continue working, it will continue to sniff data also after it is unplugged because of its rechargeable built-in battery. KeySweeper is able to store the sniffed keystrokes both online and locally on the device.usernames or URLs. While the device is logging the keystrokes he is able to continue working, it will continue to sniff data also after it is unplugged because of its rechargeable built-in battery. KeySweeper is able to store the sniffed keystrokes both online and locally on the device. KeySweeper is able to store the sniffed keystrokes both online and locally on the device.
As explained by Kamkar, this kind of devices is very simple to assemble and are very cheap, the hardware necessary to build a KeySweeper is reported below:
The FBI’s notification makes no reference to specific cases where criminals used the sniffing device.
Microsoft confirmed that sniffing attacks could be effective against any wireless device that doesn’t protect communication by encrypting data in transit, for this reason, any keyboards manufactured after 2011 is today protected by the use of the Advanced Encryption Standard.
The FBI notification also includes precious suggestions of the defense of corporations, first of all, the restriction for the use of wireless keyboards.
If the use of a wireless keyboard cannot be prevented, then be sure the device uses a strong encryption for the data transmission.
“A keyboard using AES encryption makes it more difficult to read keystrokes as there are currently no known practical attacks to read AES encrypted data.” states the notification. “Keyboards using Bluetooth are also safe from KeySweeper as it listens on a different channel than that which Bluetooth transmits. However, Bluetooth keyboards must have encryption turned on and a strong pairing PIN to protect it from a similar type of data-harvesting attack.”
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(Security Affairs – KeySweeper, FBI)