如何检测硬盘是否通过USB连接？

I am trying to write a little backup program for friends and family and want it to be as simple to use a possible. I don't want to have to ask the user where to backup their data to, I just want to search for and use the first USB hard drive connected to the computer. Obtaining the unique ID of the hard drive would probably be a good idea too, just as a double check for next time the backup runs.I am trying to write a little backup program fo