Attack IIS 7 on my Windows 2008 with Linux firewall got The service is unavailable - repost

I have a windows server 2008 running IIS 7, I get notice from a guy that said will put my site down, and now when I try open my site I see: "The service is unavailable." The internet configuration here is: Internet > Linux (Firewall iptables) > NAT 80 to > Windows 2008 with IIS 7 I need someone to configure Linux to fix solution for this kind of attack or configure windows to fix it.