Too many comments, not about my site.

I am getting thousands of comments. None of them pertain to my site. I tried turning commenting off, but they just keep coming. HostGator is threatening to drop me because I’m using too much space I guess. I think there is some kind of connection or hack from another blog or site. Please help me fix this problem. Is there an easy way to delete all comments without having to select each one, put them in the trash then empty the trash? They just keep coming!!

Wayne