No, USB keyboards (or mice) can't. That's why some keyloggers use a certain sequence of capslock/numlock/scroll-lock presses to trigger output of a menu or the

No, USB keyboards (or mice) can't. That's why some keyloggers use a certain sequence of capslock/numlock/scroll-lock presses to trigger output of a menu or the stored data: The status of the corresponding LEDs is the only information a PC sends to a keyboard.