How can I test if my apache server is an open proxy?

Solution 1:

You may verify it by using Telnet:

telnet yoursite.example.com 80
GET http://www.yahoo.com/ HTTP/1.1
Host: www.yahoo.com

Source: https://wiki.apache.org/httpd/ProxyAbuse

Solution 2:

The simple answer is this, if you have ProxyRequests On (defaults to off) somewhere in your configuration then you might be running an open proxy, if you do not then you are not, at least from the Apache configuration side of things.

If you are still getting 200 OK entries in your access log for requests that look like forward proxy requests, it is probably because you have catchall rewrites that maps any request to a controller no matter what it looks like. You could probably add conditions to prevent this if you are worried.