Experts Chart Spike in Cyber Sieges

Cyber attacks with enough firepower to knock entire countries off the Internet have spiked in recent months, raising fresh concerns within the security community about weaknesses in the Internet infrastructure that help create such weapons of mass disruption.These “distributed denial of service” or DDoS attacks use robot networks or “botnets” — many hundreds or thousands of compromised PCs — to flood targets with so much junk traffic that they can no longer accommodate legitimate visitors.
http://www.washingtonpost.com/wp-dyn/content/article/2009/05/01/AR2009050101593.html