How to detect Codeen Proxy

I have small proxy-list site and I would like to remove from my list all Codeen proxies. Do you have any idea how to detect them? (I prefer PHP language)

I tri开发者_如何学编程ed to compare proxyjudge results of codeen servers and normal proxies, but there is no diffrences.

I would be really grateful for any ideas.

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Parse out the list of all Codeen proxies and remove them from your list.