The new data comes from security vendor Prolexic, which counts ten of the world's major banks as clients for its DDOS mitigation services. In its report, the company said DDOS attacks also rose in intensity, with increases in both bandwidth and packet-per-second rates.

The average attack bandwidth rose from 5.2G bps (bits per second) in the last three months of 2011 to 6.1G bps in the first quarter of this year. But the average attack length of time dropped from 34 hours to 28.5 hours over the same periods, Prolexic said.

"The reduction in attack campaign duration, combined with an increase in mitigated bytes and packets, indicates that attackers are using shorter, stronger bursts of traffic to conduct DDOS campaigns," the company said.

Prolexic has a network of data centers that attack traffic intended for one of its clients is routed through and filtered.

More than 70 percent of the malicious attack traffic came from China. Two networks -- AS 4134, which belongs to China Telecom, and AS 4837, which belongs to China Unicom -- "take first and second place as the primary source of DDOS traffic," Prolexic reported.