• In this blog post, Pixalate explains X-Forwarded-For and the best practices as it relates to detecting, targeting and even blocking the IP addresses associated with programmatic advertising transactions to reduce ad fraud and improve quality.
  • If an SSP or exchange offering bid requests is not sending the correct IP address from the XFF header, they should be queried as to their methods of IP address detection.
  • Per the OpenRTB guidelines, Pixalate specifies using the left-most IP address in the X-Forwarded-For header as the client IP address in all transactions including targeting, filtering and blocking.

    Source: http://blog.pixalate.com/best-practices-xff-ip-address-blocking-ad-fraud