Series circuit - 3 LEDs

What Hacker News said

Recommends tzs · 2020-11 · on “MyNOR: Single board computer that uses a single NOR gate as its ALU”

It's not quite a backdoor, but don't underestimate what can be hidden in seemingly simple places: [this video] Here's how that is doing it: [LINK] He's got several more, including this one which doesn't even use switches. You just tap the wire to toggle the LEDs: [LINK] I have no idea how that one works.

Cites garaetjjte · 2018-04 · on “'Demonically Clever' Backdoor Hides Inside Computer Chip”

Obviously not at SMD scale, but I have seen fun videos with seemingly simple circuits with LEDs and switches connected in series and they behaved completely differently (eg. each switch connected in series controlled other LED). It turned out that switches and LEDs have been modified with clever frequency generators and filter circuits. edit: [this video]

Cites wanderingjew · 2018-06 · on ““All accredited journalists at the #KimTrumpSummit get a free USB fan.””

I'm not going to say 'no', but I would highly doubt it. If you're wondering what the 'state of the art' in disguising components to look like other components is, this [1] is probably the best example. It's a guy that turned a LED into an LED and an inductor, and put transistors inside of switches. What you're proposing -- basically putting a USB-capable microcontroller inside something that looks like resistor -- isn't impossible. I can imagine that it could be done, but I would have no idea how. You would probably go with a very small (physically) microcontroller, maybe one of the SOT-23-6 PIC or AVR packages. I don't think it's possible to write a USB stack for those, and you only have 1-