WASHINGTON, July 22 (Yonhap) -- The United States has been unable to trace the source of the massive cyber attacks that paralyzed a number of government and commercial Web sites in South Korea and the U.S. earlier this month, the top U.S. intelligence official said Wednesday."We have not figured out exactly who conducted that July 4th -- that attack that began on July 4th," Dennis Blair, director of National Intelligence, told a U.S. Chamber of Commerce National Security Task Force meeting.
South Korean officials suspect that North Korea was behind the attacks, although they have failed to present concrete evidence for the allegation.
Blair described as "unsophisticated" the denial of service attacks that used tens of thousands of compromised computers to launch simultaneous requests for information, temporarily rendering the Web sites attacked unreachable. "It was a relatively unsophisticated botnet-type attack that nonetheless did deny service for some Web sites in this country," he said.
The U.S. government is cooperating closely with foreign governments to determine the origins of the rare attacks, he said.
"The process of tracking it down is still going on," Blair said. "That is a good one -- back to one of our previous questions -- in which we're working with foreign partners to try to compare data to figure out if we can actually nail it down."