Advice on an Anti-Proxy Script

[Chelf12]

<?php
if (isset($_SERVER['HTTP_X_FORWARDED_FOR'])){
die("Site has detected a proxy! Site will not load any further!</body></html>");
}
?>

Sans the PHP tags, where would the best place to place a hook for that? I found the script online, and it's free for use, and I want to hook it in as a plugin or product for vBulletin. Which hook would be best to use? I got it somewhat to work with the login process, where if you login through a proxy, you get a white screen, and cannot advance, I think.

[Dismounted]

It is actually not hard to bypass that check. In fact, most proxy servers don't pass on that value anyway. And the ones that do are usually for legitimate purposes (e.g. school/work).

[Chelf12]

Ah. The reason I was wondering, is because we have alot of people on our site bypass their bans through proxies, and they are PERSISTENT. IE, majority of them will go 2 months before giving up.