Someone copied my exact website

Hey - I know this is a pretty random question but I'm not sure who else to ask...

Today I was looking at my Google Analytics and found a bunch of referral traffic from to my website

You'll see that the referring site is somehow an exact copy of mine!

Does anyone know how they are doing this and/or what I should do about it???

Again, I know this isn't WPMU-related but I'm not sure who else to ask.