Well, it should be possible to hide components inside the PCB, see: (1) https://hackaday.com/2017/09/11/the-components-are-inside-the-circuit-board/ https://ha

Well, it should be possible to hide components inside the PCB, see: (1) https://hackaday.com/2017/09/11/the-components-are-inside-the-circuit-board/ https://hackaday.com/2017/09/11/the-components-are-inside-th... (2) https://hackaday.com/2019/01/18/oreo-construction-hiding-your-components-inside-the-pcb/ https://hackaday.com/2019/01/18/oreo-construction-hiding-you... Analysis should be quite difficult; if you hide them between copper layers, or worse behind components and behind copper layers, I believe it'd require vert inspection with x-rays to detect. The main question is that of utility. Data exfiltration is highly unlikely. It's possible to trigger malfunctions, but it's not clear this would be useful (when triggered at a certain date, randomly, etc) -- it would be easy to detect and cause the companies to switch to suppliers. I think the main possibility/atractivity would be some kind of radio activation of malfunction. But then you need a significantly sized antenna [1] and a very strong signal to penetrate the circuit shielding (which is probably emp-resistant). But the main impediment I think is the total erosion of trust in Chinese manufacturing this could bring. Most of the world manufactures in China and they don't want to change this. They wouldn't sacrifice this trust except at a very good opportunity. The same goes from a strategic spying perspective: don't use bugs frivolously or you'll risk raising the awareness level compromising important opportunities. [1] Which cannot be hidden between layers, although it might be possible to use some of the traces themselves as antennas. If the pcb has an obvious external antenna I/O then of course this would make things easy. All that said, it does make sense to keep an eye on this possibility, but probably not in this particular case.