TTinCo-
Thanks for the compliment. I've just picked up a few things here and there. I can usually think of a way to do something (to convince myself it is possible), though the hackers would use a much more sophisticated method than would occur to me.
I try to ask a lot of questions and get an idea of what is possible or the general principles. I'm more of a Jack-of-All-Trades (master of few) kind of guy. Fortunately, I'm often able to bridge the gaps between a software expert and a hardware expert by getting them to work together better.
Ebay, Yahoo, Microsoft, etc. spent millions handling and solving these types of DOS problems. Find out what they did and BUY THAT SOLUTION. I'm sure it costs less than $30K.
TTinCo, with your knowledge of the network side, do you know who the ISP's are for the different books affected? I ask because some ISP's may be immune to the attack. On the other hand, if 5 books all use the same ISP, they could chip in and buy the ISP the additional equipment to put upstream. (5 books x $30K is buys a lot of hardware for the ISP)
Anyway, try to compile a list (don't post it, as it may give the hackers useful information). Eventually, if a pattern emerges, you can contact the books and ISP's directly. I'm sure the ISP's are all over this and may noticed other patterns.