Debugging mechanisms like JTAG (IEEE1149.1) first appeared in the 1980s . Over time, microchip vendors extended the functionality of these interfaces. This allowed developers to obtain detailed information on power consumption, find bottlenecks in high-performance algorithms, and perform many other useful tasks.
Hardware debugging tools are also of interest to security researchers. These tools grant low-lev el system access and bypass important security protections, making it easier for researchers to study a platform's behavior and undocumented features. Unsurprisingly, these abilities have attracted the attention of intelligence services as well.
For many years only a limited audience had access to these technologies for Intel processors, due to the need to own expensive specialized equipment. But with Skylake processors, the situation changed in a big way: debugging mechanisms were built into the Platform Controller Hub (PCH), which opened up this powerful tool to ordinary users, including malicious ones, who could use it to gain total control over the processor. For security reasons, these mechanisms are not activated by default, but as we show in this article, they can be activated on the equipment sold in common computer stores.
Read full research here: www.ptsecurity.com/upload/corporate/ww-en/analytics/Where-theres-a-JTAG-theres-a-way.pdf