After analysing traffic from 68 ISPs around the globe, a security researcher claims that as much as five percent of all Internet traffic is from DDoS-attacks.
Since beginning the research, Arbor Network's chief research officer Danny McPherson claims there were over one million denial of service attacks -- roughly 1,300 per day -- across the ISP networks involved in the study, which has already run for 18 months.

http://www.zdnet.com.au/news/securit...9287902,00.htm