A unique data-stealing trojan has been spotted on USB devices in the wild – and it is different from typical data-stealing malware. Each instance of this trojan relies on the particular USB device on which it is installed and it leaves no evidence on the compromised system. Moreover, it uses a very special mechanism to protect itself from being reproduced or copied, which makes it even harder to detect.

http://www.welivesecurity.com/2016/03/23/new-self-protecting-usb-trojan-able-to-avoid-detection/