Do they still make non-USB mice/keyboards? I am also wondering if the CEC HDMI protocol could be exploited. Plugin a nefarious monitor which can send a payload and receive a graphic stream back with the response.
We used a Dell workstation laptop, which has ECC memory and a Xeon processor like a server. Built-in keyboard and trackpad reduces the risk of random external devices needing to be used.
Protection was BitLocker drive encryption with a manually entered (long!) passphrase to decrypt. Backups were to encrypted USB media never plugged into anything else other than a redundant clone of the CA used for DR testing. Everything went into safes.
This design works Well Enough for all but the most demanding purposes, but the whole rigmarole was undone by a well-meaning but naive admin “just doing his job”.
Yup. PS2 keyboard and mice are still easy to find. As are VGA monitors. If you are super paranoid, you still need something more, as both PS2 and VGA allow for bidirectional transfer. But, at a certain point you need to trust your supply chain. If someone can tamper with your new monitor, they can probably tamper with your new server as well.
Even without compromising the host, you wouldn't want a monitor mirroring the output to an attacker, or a keyboard mirroring every stroke.
