X-Forwarded-For - how to properly and securely handle this header?

The article discusses the X-Forwarded-For (XFF) header, which is a critical part of the web application landscape, especially for users accessing services through a proxy or load balancer. XFF is an HTTP header that enables servers to determine the true client IP address, even when the connection is made via intermediary servers. The author explains how this functionality can impact both security and server load, highlighting the most common applications for this header. While it provides important analytics information, it also brings risks of misuse if not properly secured. Website owners should be aware of the threats associated with XFF and implement practices such as data validation to protect their systems. The article also includes examples of implementation and tips on how to properly utilize this header to effectively manage web traffic in a secure and efficient manner.