WASHINGTON: US authorities say they are eyeing the Democratic People's Republic of Korea (DPRK) as the origin of the cyber attack that overwhelmed government websites in the United States and the Republic of Korea (ROK). But they warned it will be difficult to quickly identify the attackers.

The powerful attack that stretched on for days over the holiday weekend targeted dozens of government and private sites, and underscored how unevenly prepared the US government is to block such multipronged assaults. While Treasury Department and Federal Trade Commission websites were shut down by the malicious software attack, others such as the Pentagon and the White House were able to fend it off with little disruption.

The DPRK link, described by three officials, more firmly connected the US attacks that began July 4 to the cyber assault Tuesday on government agencies in the ROK. The officials said that while Internet addresses have been traced to the DPRK, that does not necessarily mean the attack involved the Pyongyang government.

The officials spoke on condition of anonymity because they were not authorized to speak publicly on the matter.

The ROK intelligence officials have identified the DPRK as a suspect in those attacks and said that the sophistication of the assault suggested it was carried out at a higher level that just rogue or individual hackers.

US officials would not go that far, and publicly declined to discuss who may have instigated the intrusion or how it was done.

In an Associated Press interview, Philip Reitinger, deputy under secretary at the Homeland Security Department, declined to discuss the origins of the attack.

The fact that a series of computers were involved in an attack, he said, "doesn't say anything about the ultimate source of the attack."

"What it says is that those computers were as much a target of the attack as the eventual websites that are targets," Reitinger said. "They're just zombies that are being used by some unseen third party to launch attacks against government and nongovernment Web sites."

Reitinger, who heads DHS cybersecurity operations, said the far-reaching attacks demonstrate the importance of cybersecurity as a critical national security issue.