Name: Forbid Proxies
Version: 1.1
Description: Denies POST Request using a Proxy Server. Can access site, but not comment. See <a href="http://perishablepress.com/press/2008/04/20/how-to-block-proxy-servers-via-htaccess/">Perishable Press</a>
Rules: 
RewriteCond %{HTTP:VIA}%{HTTP:FORWARDED}%{HTTP:USERAGENT_VIA}%{HTTP:X_FORWARDED_FOR}%{HTTP:PROXY_CONNECTION} !^$ [OR]
RewriteCond %{HTTP:XPROXY_CONNECTION}%{HTTP:HTTP_PC_REMOTE_ADDR}%{HTTP:HTTP_CLIENT_IP} !^$
RewriteCond %{REQUEST_URI} !^%relative_root%(wp-login.php|wp-admin/|wp-content/plugins/|wp-includes/).* [NC]
RewriteCond %{REQUEST_METHOD} =POST
RewriteRule .* - [F,NS,L]