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Open Resolver Problems
On 2013-03-25, at 12:35, Alain Hebert <ahebert at pubnix.net> wrote:
> Why would you only go after them?
> Easier target to mitigate the problem?
> That might be just me, but I find those peers allowing their
> customers to spoof source IP addresses more at fault.
> PS: Some form of adaptive rate limitation works for it btw =D
DNS servers (recursive and authoritative-only) are the low-hanging fruit du jour. I agree that there are many other effective amplifiers, and that even maximum DNS hygiene will not make the wider problem go away.
A quick note on your final comment, though: whilst adaptive response rate limiting (so-called RRL) is fast developing into an effective mitigation for reflection attacks against authority-only servers, there is far less experience with traffic patterns or the effects of rate-limiting (using RRL or anything else) on recursive servers.
The best advice for operation of recursive servers remains "restrict access to legitimate clients", not "apply rate-limiting".