Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I setup a simple reverse proxy with mod_rewrite [P]. Is this detectable in any way? I did not see any proxy related headers passed back to the client. Curious if there's any other way someone could detect that the request has been proxied.

share|improve this question
Can you clarify what you're looking to hide? The mere fact that a request is being proxied shouldn't be sensitive. With an Apache proxy, there are always going to be certain conditions (issues with the upstream server) that will reveal the proxy's presence. – Shane Madden May 16 '12 at 17:47
It is sensitive in this situation. I simply want to know if anyone could detect that the request was proxied. What are these certain conditions you speak of? – Moonstone May 16 '12 at 18:25
up vote 2 down vote accepted

If the upstream is unreachable or just loses a single connection, the user will get a proxy-specific 502 response code.

Assuming that your RewriteRule is only proxying for a subset of the URL space in the domain, you may have subtle header differences, differences in the handling of file caching and encoding (especially if the content on the upstream server is a different web server or a different kind of content, like PHP for instance), or even clock differences in the returned responses.

In most cases, a user will not know or care that a request has been proxied, and will not notice with a cursory glance at the headers. However, a user the knows what to look for and is determined to find evidence that a request is being proxied will almost certainly be able to do so, either through careful comparison of response behaviors and handling of edge case and error-inducing requests, or by stressing the server into simply throwing a 502.

share|improve this answer
Ok, got it. In my case the entire domain is proxied so I would just worry about 502's. Good info Shane, thank you! – Moonstone May 16 '12 at 19:19

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.