Schneier on Security: Backdoor Found (Maybe) in Chinese-Made Military Silicon Chips
tells a tale of chips "manufactured in China", that could be "infected". The chip in question is "prevalent in many systems from weapons, nuclear power plants to public transport".The publicizers of this vulnerability appear quite proud of their discovery and reverse engineering skills.
The chip in question is a type of programmable device (FPGA), hence the assertion that it is used in such a variety of applications. And, the back door is apparently related to the JTAG port.
Check out the story and the insightful comments. I'm inclined to think this is a tempest in a teapot, but it's an interesting topic to ponder.
If such a problem needs solving, a company that I met at DAC may have just the solution. Check out SypherMedia International for all your circuit obfuscation needs!