In later versions, starting from Skylake and Kabylake processors, Intel simplified the connection process and introduced DCI (Direct Connect Interface) which allows JTAG access via the USB 3.0 port present on the machine. This is handy in the case of portable computers like laptops.
According to the Positive Security researchers, Maxim Goryachy and Mark Ermolov, the ability to access CPUs via the USB port can be dangerous. They note that the target computer could be tagged as vulnerable even if the DCI interface is just enabled, there are no software or hardware changes to be made. However, DCI is disabled by default on Intel CPUs. It can be enabled using the BIOS configuration, and a proprietary key is required to access JTAG.
The duo Goryachy and Ermolov demonstrated the vulnerability – at the Chaos Communication Congress (33C3) last year – which can be used to gain full control of the Intel CPUs. They believe that CPU access mechanisms like this can take destructive USB devices, like Killer USB, to a whole new level.