My apple thunderbolt 4 cable has a computer more powerful than my firs computer in it (ARM Cortex‑M0 core running at up to 48 MHz vs a 286 at 25mhz)
Adam Savage's Tested : Look Inside Apple's $130 USB-C Cable - https://www.youtube.com/watch?v=AD5aAd8Oy84 (1 minute in "we've been saying that our phones have more computing power than the Apollo guidance computer but I'm positive now that this cable has more computing power than the Apollo guidance computer")
That video is a look at cables (not just Apple's) with Lumafield's CT Scan.
It's a good watch, and I learned some new stuff about some things that I only knew a little bit about before.
Thanks!
A concern: with all this computing onboard, does this mean a malicious USB-C cable could record screen and keystroke?
Often the keyboard receiver is plugged into the monitor's USB hub and so screen and HID are both going along a single cable ... Which also does power delivery. Such cables are a definite "sales category" and could be a target for supply chain attacks. But if they now have chips onboard, doesn't that mean an attacker could even takeover a genuine cable? It seems like a real risk tbh.
It is possible that the tech exists, but isn't yet at a point that it can be easily mass-produced, which means "spy cables" may actually be available, from Q-types.
Keystrokes: Easily. At least for USB 3 and 4, USB 1/2 data is a physically separate channel that just happens to almost always be packaged alongside the faster stuff, so the lower speed stuff like input devices is easy to intercept. I don't know if Thunderbolt does the same or not, normally USB-C alternate modes still keep the USB 2.0 signals available but Thunderbolt might be an exception.
Screen: Probably not modern video modes in a purely stealthy cable formfactor *YET*, at least not using COTS parts, but it wouldn't surprise me to find the secret squirrel types either already have it or are working on it.