A topic scheduled to be presented during Blackhat 2014 deals with malicious actions that could originate from USB devices that have been altered to exfiltrate data from any computer that they are attached. The condition is not limited to only USB storage devices. It can also be performed on USB hardware such as keyboards, mice and potentially even cell phones that have been attached to a computer that has previously had an altered USB device attached. The information as it is currently know is available from the URLs below. Additional information might be available after the presentation. However, as it is currently understood, there is no ability to patch a workstation against this exposure other than only using USB devices that you can confirm the origin of.
http://www.wired.com/2014/07/usb-security/