ShadowBr0ker

It could also be that you've accidently hit the keyboard combination "SHIFT" + "ALT". If your system has saved the US and EU Keyboard layout, then you can switch between these two. Letters like "z" or "y" will switch place or some symbols like "_", "-", " ; " or " : " will be reassigned to other keys to match the changed layout. But since it is masked like ******, you most likely don't notice it while typing.