IDG Answers is a community of experts who are passionate about technology. Ask a question or answer one below.
There is an article here on IT World about this attack that you might like to check out.
Here is a description of these types of attacks from US-CERT that you also might find useful:
"Recently, certain UDP protocols have been found to have particular responses to certain commands that are much larger than the initial request. Where before, attackers were limited linearly by the number of packets directly sent to the target to conduct a DoS attack, now a single packet can generate tens or hundreds of times the bandwidth in its response. This is called an amplification attack, and when combined with a reflective DoS attack on a large scale it makes it relatively easy to conduct DDoS attacks."