A third wave of cyber attacks hit government and private websites yesterday, some of which reported access disruptions or temporary paralyses.

The attacks, which began around 6 p.m., targeted half a dozen sites including the Ministry of Public Administration and Security's electronic government site, Kookmin Bank and the nation's leading portal sites such as Naver and Auction, said officials at the state-run Korea Information Security Agency.

But the damage seemed relatively limited, they said, as many of the site operators braced for the latest round of distributed denial of service assaults after prior warnings from antivirus companies.

Kookmin Bank said it was forced to shut down its internet banking site for about 30 minutes until 6:30 p.m. after the site came under the DDoS attack from unidentified hackers. But most of the other sites were little affected by the attacks, maintaining normal operations.

Despite emergency meetings and other follow-up measures, the government was still unable to fend off the attacks completely.

"This particular method of cyber attack is virtually impossible to avoid," said one Foreign Ministry official in charge of IT and communications.

Beginning Tuesday, the DDoS attacks have overwhelmed major websites here and in the United States. Unidentified hackers began their initial attacks at 6:00 p.m. Tuesday, blocking internet users from accessing 26 websites including the White House and Cheong Wa Dae.

Speculation is split over the culprit behind the cyber attack, with some experts here now fingering hackers in the United States.

Hong Min-pyo, CEO of a local security software firm Shiftworks yesterday raised the possibility of the distributed denial of service attacks originating from a locale in the United States, which also was hit by the attacks.

Hong cited analyses conducted on the virus, saying the masterminds appeared to be "tech-savvy."

The National Intelligence Service on Wednesday reportedly told lawmakers that North Korea may have manipulated the attacks.

Some lawmakers are now calling to pass a moored bill for more stringent regulation on cyber terrorism.

"The time has come to seriously consider passing this law as key government organizations and websites are apparently vulnerable," said Gong Sung-jin, a Grand National Party legislator yesterday.

The Prime Minister's Office yesterday held an emergency meeting to help prepare for further aggression, and also analyze the damage so far.

The Korea Communications Commission has now placed a request with local information communication service providers to ban internet access from the so-called "zombie" computers via which the latest distributed denial of service virus was unleashed.

Up to 29,000 personal computers appear to have been used as vehicle for the virus, according to the National Police Agency.

Recent government data showed that the administration becomes vulnerable to cyber attacks over 20 times daily. The Defense Security Command said last month that the military network was subject to up to 95,000 such attacks everyday.

Those who suggested North Korea as the culprit said Pyongyang had for years been honing its cyber capabilities

"Our understanding is that North Korea has been training individuals for cyber warfare over the past few years," said one defense industry researcher who declined to be identified.

The Korea Computer Center of the Kimchaek University of Technology, he said, likely handle most of such training.

North Korea may have established such forces as early as 1998, with up to 12,000 personnel conducting missions, according to Kevin Cole, a former Netscape chief strategist and strategic advisor with the Technolytics Institute in the United States.

Critics warned against politicizing the latest cyber infections.

Main opposition Democratic Party lawmakers protested the passing of the anti-cyber terrorism bill citing invasion of privacy and internet censorship.

They also called for the government to offer concrete evidence to prove that North Korea was involved in the latest attacks.