I think at this point pretty much anything on your PC is backdoorable. I can't think of a single device in my computer that doesn't respond to "magic I/O packet

I think at this point pretty much anything on your PC is backdoorable. I can't think of a single device in my computer that doesn't respond to "magic I/O packets" which are undocumented (obviously) and prone to bugs (possibly). Gaming mouse? Yeah send some I/O packets and you can change the DPI, USB update rate, whatever. A write-protected USB device? Uh-huh, send some magic-packets to the controllers to reset it/format it/whatever (Recently did this with one of those Dell USB Mentor Media drives that they ship the OS on). Access point? Yeah, send some magic packets and you can set the password/SSID/whatever. Hard Disk? undocumented SATA commands allows for reprogramming. This is just the 'easy' way, without going into JTAG and other diagnostic interfaces.