Any config tricks to stop site from framing us?

[Ian Evans]

Yesterday, I discovered that someone had registered a site (basically 
taking our domain name and adding a word to it) and then framed our 
whole site in theirs. By that I mean it's a full iframe job, with no 
toolbars showing.

Not sure what they're up to, but I'd like to stop it. I know I can use 
a framebuster, but I'm wondering what I can do on the nginx.conf end to 
stop them dead in their tracks so not an ounce of our bandwidth goes to 
them.

Thanks for any advice.