North Korea is suspected of playing a part in the latest round of cyber attacks that paralyzed government networks and leading portal servers, sources quoted the National Intelligence Service (NIS) as saying in a briefing to lawmakers Wednesday.

A dozen Internet sites, including those run by Cheong Wa Dae, the National Assembly, the Ministry of National Defense and top Web portal Naver, were hacked with their sites down from Tuesday evening to Wednesday morning.

China, North Korea and Russia were initially thought to be possible culprits. But the NIS briefed the lawmakers about its analysis that tentatively concluded that Pyongyang or its sympathizers were behind the cyber attacks. It was not immediately available how the NIS came to such a conclusion.

Earlier in the day, the Korea Communications Commissions (KCC), the nation's telecom regulator, said tracking will be difficult as DDoS attacks, by nature, are hard to pin down as they involve a huge number of sources.

Several major US and South Korean government websites were disabled by a North Korean denial of service attack beginning on July 4.

Others familiar with the U.S. outage, which is called a denial of service attack, said that the fact that the government Web sites were still being affected three days after it began signaled an unusually lengthy and sophisticated attack. The officials spoke to The Associated Press on condition of anonymity because they were not authorized to speak on the matter.

North Korea devotes nearly all of its resources to military and nuclear efforts, and cyberspace is simply another battleground. It would be unwise to underestimate the North Korean ability to launch cyberattacks on government websites, particularly DoS attacks, given that there are hacking communities that devote themselves to discussing these very scenarios.

That's on the heels of a report saying that US cyberdefense systems don't work. In fact, the latest iteration of the system (Einstein 2), which alerts officials that an attack is underway, isn't going to be ready for another 18 months. The system can't thwart attacks that it isn't familiar with. One of the biggest problems is concerns over privacy, particularly since the system is being rolled out on telecommunications networks operated by various companies, including AT&T. A third iteration of Einstein may be able to thwart attacks, but there's no roll-out date.

Then again, federal authorities aren't doing much better in protecting government buildings as undercover investigators had no problem sneaking bomb materials into federal buildings.

WASHINGTON - The powerful attack that overwhelmed computers at U.S. and South Korean government agencies for days was even broader than initially realized, also targeting the White House, the Pentagon and the New York Stock Exchange.

Other targets of the attack included the National Security Agency, Homeland Security Department, State Department, the Nasdaq stock market and The Washington Post, according to an early analysis of the malicious software used in the attacks. Many of the organizations appeared to successfully blunt the sustained computer assaults.