How to Block Proxy Servers via htaccess

.htaccess made easy

Not too long ago, a reader going by the name of bjarbj78 asked about how to block proxy servers from accessing her website. Apparently, bjarbj78 had taken the time to compile a proxy blacklist of over 9,000 domains, only to discover afterwards that the formulated htaccess blacklisting strategy didn’t work as expected:

deny from proxydomain.com proxydomain2.com

Blacklisting proxy servers by blocking individual domains seems like a futile exercise. Although there are a good number of reliable, consistent proxy domains that could be blocked directly, the vast majority of such sites are constantly changing. It would take a team of professionals working around the clock just to keep up with them all.

As explained in my reply to bjarbj78’s comment, requiring Apache to process over 9,000 htaccess entries for every request could prove disastrous:

The question is, even if you could use htaccess to block over 9,000 domains, would you really want to? If you consider the potential performance hit and excessive load on server resources associated with the perpetual processing of such a monstrous list, it may inspire you to seek a healthier, perhaps more effective alternative..

A better way to block proxy servers

Rather than attempt to block proxy servers by who they are (i.e., via their specified domain identity), it is far more expedient and effective to block proxy servers by what they do. By simply blacklisting the various HTTP protocols employed by proxy servers, it is possible to block virtually all proxy connections. Here is the code that I use for stopping 99% of the proxies that attempt to access certain sites:

# block proxy servers from site access
# http://perishablepress.com/press/2008/04/20/how-to-block-proxy-servers-via-htaccess/

RewriteEngine on
RewriteCond %{HTTP:VIA}                 !^$ [OR]
RewriteCond %{HTTP:FORWARDED}           !^$ [OR]
RewriteCond %{HTTP:USERAGENT_VIA}       !^$ [OR]
RewriteCond %{HTTP:X_FORWARDED_FOR}     !^$ [OR]
RewriteCond %{HTTP:PROXY_CONNECTION}    !^$ [OR]
RewriteCond %{HTTP:XPROXY_CONNECTION}   !^$ [OR]
RewriteCond %{HTTP:HTTP_PC_REMOTE_ADDR} !^$ [OR]
RewriteCond %{HTTP:HTTP_CLIENT_IP}      !^$
RewriteRule ^(.*)$ - [F]

To use this code, copy & paste into your site’s root htaccess file. Upload to your server, and test it’s effectiveness via the proxy service(s) of your choice. It may not be perfect, but compared to blacklisting a million proxy domains, it’s lightweight, concise, and very effective ;)