> All it takes is to throttle traffic from the resovers to outside the > ISP network to a reasonably low value. Depending on the ISP this is > usually in the low Kbits. All it takes is a moderate amount of > competence in the ISP:
I don't believe this would help the problem. One of the notable features of many reflected attacks is that no single reflector is hit with a large amount of traffic. It is spread out amongst many many reflectors so that the reflectors don't notice the issue, and so that the victim has a harder time filtering the traffic. If your goal is to eliminate the recursive resolution reflection amplification, then you must disable it for all but trusted subnets. This also defends the server from the more trivial of cache poisoning attacks (assuming your own systems use the resolver as well). tim
