Arduino uno + motor shield power problems

Hi! I made diy windsim using arduino uno + motor shield for my simulator and i powered it with 12v 1.5A power supply and connected it to my pc using usb hub ( there is 2 rgb light strips in same hub) and when i plug in my power supply it will supply power to that usbhub so those rgb lights light up eventho my pc is off, so my guestion is how harmful this is to my pc if any ??

Is there an Arduino involved somewhere ?