There are ways to fight the DoS attacks with hardware, software and bandwidth bursts...but it's a case-by-case situation.
Using
Linux Firewalls instead of Microsoft ISA servers and ANY Microsoft product or related product makes ALL the difference.
STOP using Microsoft products for your Internet Security and these DoS attacks will just about DISSAPPEAR as these DoS attackers and Hacks only Know Microsoft and all it's flaws.
I know of several BIG companies that get DoS attacks everyday but they have NO PROBLEMS as they have studied the attacks and KNOW how to block them.
If allot of books are still having problems they need to EMPLOYEE a better Internet Security company and this will come to an end.
But it seems that
some books don't want to admit they need better and more experienced Internet Security Specialists.
Here are some link to some hardware that helps but there are even better units out there:
http://www.toplayer.com/content/products/intrusion_detection/attack_mitigator.jsp
Nokia makes one of the best units out there as well