IoT Penetration Testing Cookbook

JTAG identification

The last thing that we will look for in order to identify interesting exposed interfaces on the device is a Joint Test Action Group (JTAG).

JTAG is a simplified way of testing pins and debugging them compared to the previous way of bed-of-nails testing. It allows device developers and testers to ensure that each of the pins in the various chips on the device are functional, interconnected, and operational as intended.

For penetration testers, JTAG serves a number of purposes, ranging from giving us the ability to read/write data and even debug running processes, and modifying the program execution flow.

The four most important pins when we are looking for JTAG are test data in (TDI), test data out (TDO), test clock (