well, it makes a lot of man in the middle : the HW USB susbsystem, the USB driver, the OS, the driver or the electronic doing the interface. Plus it makes a lot

well, it makes a lot of man in the middle : the HW USB susbsystem, the USB driver, the OS, the driver or the electronic doing the interface. Plus it makes a lot of electromagnetic vulnerabilities (reading/influencing with a magnetic field) A purely paranoid person would really prefer something with an antenna (to get some noise by detection), some RLC, a defective/chaotic oscillator on the dye of an a SOC that makes it embedded and you can verify by looking with a microscope that you shield in a Faraday cage. And no, deciphering logic of a microchip with a microscope is not that hard ; almost anyone can do it with a tad of training and some education.