One related idea I had at lunchtime is this: suppose the bot attempts to crawl your directory structure. Having detected it's a bad bot. Is there a way to make its client machine cache a recursive directory structure? (or a false picture of one induced by artificial response). I am not sure how caching works at a lower level - it's just a functional idea. But if so, then the bot would be crawling its own cache forever, rather than bothering your real machine with it.