Detecting proxies and VPNs can help prevent fraud, abuse, and skewed campaign data. However, blocking all proxies would significantly impact sales conversions and could have an unintended negative impact on your users. The best solution is to monitor proxy traffic and only block suspicious IP addresses.

Proxy detection test are useful for many legitimate purposes, such as improving website performance and maintaining privacy. But, they are also popular with fraudsters and cybercriminals for masking their identity, spoofing their location, and conducting other malicious activities.

Proxy Detection Test: How to Identify VPN and Proxy Users

Traditional methods of detecting proxies are often over-sensitive and cause false positives. Residential proxies (such as those provided by cable and satellite providers) use standard web ports, making them difficult to distinguish from other traffic. Additionally, if a user’s router is compromised, it can serve both their legitimate traffic and proxy activity, creating an even more indistinguishable threat.

More advanced detection systems examine a packet’s content on a deeper level, inspecting information beyond headers to identify patterns associated with proxy and VPN use. This is called device fingerprinting and works by examining aspects of a packet’s content (e.g., protocols, headers) and comparing them to a list of known patterns.

Other advanced detection technologies analyze a packet’s latency by measuring the time it takes to receive responses from various proxy servers. This can reveal differences in connection speeds that are often caused by proxy or VPN use. This technique is sometimes combined with other features to identify proxy users, such as analyzing a packet’s User-Agent or looking for X-Forwarded-For HTTP headers that reveal the original client IP address.