When using a web scraper, you will likely be connecting to websites via a proxy. This process hides the actual communication between your device and the website, preventing them from knowing who you are. It’s also an easy way to bypass security measures and access protected information.

To detect connections made via a proxy server, you can use the PHP proxy connection detection test. This test checks for specific proxy headers and denies the request if it sees them. The downside of this approach is that it doesn’t work against all proxies (e.g. cellular networks and select CDNs like Cloudflare).

Other methods to check for proxy connections include checking the browser and system fingerprint. These can be based on the User-Agent or cached Entity Tag identifiers, which can reveal details about your browser and operating system. Another option is to compare the latency between the server and the browser. However, this method can be manipulated by various network conditions such as WAN / DNS slowdowns and unexpected networking issues on the client side.

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Finally, you can use a port scan and blacklisting to block connections. This method is simple but effective and widely used by major sites. The downside of this approach is that it can be easily evaded by sophisticated proxies and VPN services. A better solution is to use a proxy detection API service that provides more robust, accurate, and scalable results. This also eliminates the need for you to build your own code and maintain an expensive database of blacklisted IP addresses.