Well, yes and no. They could make the argument that in "internet scale" (sic) that still qualifies as "few" (at least when compared to the number of open DNS re

Well, yes and no. They could make the argument that in "internet scale" (sic) that still qualifies as "few" (at least when compared to the number of open DNS resolvers). On the other hand, the number of open DNS resolvers used in the attacks described in the presentation (slides 7/8) were around 30K, and with a much smaller amplification factor, so these numbers can still do some damage. It would be interesting to know if there have been "hybrid" DDOS attacks, utilizing multiple spoofed-origin+amplification methods.