truth is there is no way to prevent a DOS. you can mitigate the damages in many cases, but if someone is determined, they can probably find a way to take you down. ultimately if you only have a 100Mbit NIC, and they hit you with 100Mbit/s traffic, you're down.
that module won't prevent a DOS very well, and may make debugging your site a lot harder. your visitors will complain of random 403 errors and you won't necessarily know why they're getting them.
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