2

I know the "USB Rubber Ducky" pretends to be a keyboard toward the OS, but I still don't understand how he can launch a script...

Normal keyboard can't just initiate keypress by itself right? Or maybe a special kind of driver is required?

  • Well, it can send keystrokes, so that is what it does, on windows lets send win+r c m d return e c h o space " H e l l o space W o r l d " return – ewanm89 Jun 20 '16 at 13:00
  • 1
    As for sending keystrokes itself, why not, modern keyboards have a microcontorller that sends the keycode when button is pressed, why not just have it send a predefined list programmed into it instead? – ewanm89 Jun 20 '16 at 13:03
  • @ewanm89 You said "modern keyboards". Can you give more details please? I personnaly think that all keyboard proceed like this. – Duke Nukem Jun 20 '16 at 13:17
  • Pretty much any keyboard you buy today will probably be a microcontroler. First keyboards were directly wired to CPU, no multiplexing, one line for every key (think early telnet terminals), then specialist integrated circuits were used for this PS2, 9-pin serial, USB, some cheaper keyboards may still use them (farnell.com/datasheets/79209.pdf). However higher end keyboards certainly use standard micro-controllers with just keyboard specific programming now it's pretty much just as cheap and allows the addition of various functions. – ewanm89 Jun 20 '16 at 13:25
6

When you press a key on a normal keyboard, the keyboard sends a message to the computer over USB that a key is pressed. A BadUSB device can send that same message. Instead of waiting for a keypress, it sends a couple of these messages after it has been plugged in.

So a BadUSB device doesn't just immitate a keyboard, it immitates a keyboard that has certain keys pressed in a certain order. The attacker can program a microcontroller with USB port to behave as a keyboard and press some keys after some time.

  • 1
    I think it is worth stating that there are other attack vectors available to USB devices. However, Keyboard Emulation is one of the easier options. – Bryan Field Jun 20 '16 at 13:13
  • 2
    Good point. A USB device can for example pretend to be a networking device and change your DNS server, so that the attacker can intercept all your network traffic. – Sjoerd Jun 20 '16 at 13:16
  • 1
    What's more, emulate a USB hub, and then you can emulate multiple devices off it simultaneously. – ewanm89 Jun 20 '16 at 13:27
  • 1
    Do these attack vectors are commonly used ? – Duke Nukem Jun 20 '16 at 13:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.