A report by Arbor Networks indicates somewhere between 1 and 3 percent of all Internet traffic is meaningless packets of information, used in distributed DDOS attacks:
Those are the findings of Arbor Networks, a network traffic analysis company that recently looked at traffic flowing between more than 68 Internet service providers to see how much of it was malicious.
"The thing that's surprising is it's consistently 1 to 3 percent," said Danny McPherson, Arbor's chief research officer. "It's pretty significant."
To purchase the bandwidth that Arbor tracked in these DDOS attacks, a legitimate user would have to pay hundreds of thousands of dollars per month, McPherson said.
That's not a problem for criminals, however, who use the network connections of their victims to attack others.
DDOS attacks try to overwhelm the victim's servers with routine Internet messages. Attackers try to send so many packets that the victim's computers are unable to do their regular job -- serving Web pages or sending e-mail, for example. They have become a common occurrence in recent years and have spawned a cottage industry of companies that try to mitigate their effects.
Studying the data from about 1,300 routers over 18 months, Arbor found that the tidal waves of SYN or ICMP (Internet Control Message Protocol) packets used in DDOS attacks rarely dropped below 1 percent of all traffic and could easily rise to 6 percent during peak periods.
More info at Yahoo News. In case you're wondering what attracts most DDOS attacks: its IRC servers.