Require everyone who wishes to visit your web site to apply, in person, for a web key. Surgically embed a key-generating mini-computer just under their skin. Rig it to explode if tampered with.

That should be reasonably tamper-proof. You may have a few user-acceptance issues to work out, however...

In reply to Re: If CAPTCHA isn't the answer. What is? by Anonymous Monk
in thread If CAPTCHA isn't the answer. What is? by BMaximus

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