Except it won't catch spammers that know this trick, and fill in their own X-Forwarded-For header. With bad guys, you cannot trust *anything* they send, and that includes almost all HTTP headers (the only time there are HTTP headers you can trust when receiving requests from baddies is if the baddies go via a proxy, the proxy inserts the headers, and you trust the proxy - for instance, you might want to decide to trust the aol proxies, and hence the headers they insert).

In reply to Re^3: Recognizing repetitive spammers using a time base method by Anonymous Monk
in thread Recognizing repetitive spammers using a time base method by Hagbone

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