Detection & trust · glossary

Proxy header leakage

Proxy header leakage is the disclosure of proxy use, or of the client's real address, through HTTP headers such as X-Forwarded-For, Via, Forwarded or X-Real-IP that some proxies add to forwarded requests. It only affects plain HTTP, since a proxy cannot alter the encrypted content of an HTTPS request, and it is the defining difference between transparent, anonymous and elite proxies.

1 min read Also called X-Forwarded-For, Via header Updated

Protocols All terms

Checklist#

  1. Fetch a header-echo endpoint over plain HTTP through the proxy and read every header.
  2. Any X-Forwarded-For, Via, Forwarded or X-Real-IP is a leak; the request should carry only what your client sent.
  3. Also check what your own client adds: some libraries set revealing user agents or Proxy-Connection headers.

Headers your client should not send#

Proxy-Connection, stale Proxy-Authorization values and library-default user agents identify automation as surely as a proxy header does. Set headers deliberately and consistently with the browser you imitate.

How it works at Proxy Cyber#

Proxy Cyber gateways remove proxy-related headers arriving from the client and add none toward the destination; the request reaches the target exactly as an elite proxy should deliver it.

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