WASHINGTON -- North Korea or its sympathizers were likely responsible for the cyberattack against South Korean government and banking websites earlier this year, according to a report, and the attack appears to have been linked to the 2009 massive computer-based attack that brought down U.S. government Internet sites.

A study by computer-security software maker McAfee concludes that the attack that targeted more than two dozen sites in South Korea was a type of reconnaissance mission to see how quickly the South's government detected and resolved the problem. The McAfee report said clues suggest the attack was probably engineered by the North or its sympathizers.

It is difficult to tell who was behind the attacks, Dmitri Alperovitch of McAfee told The Associated Press. But he said a review of the 2009 and 2011 attacks shows with 95 percent certainty that they were done by the same perpetrator.

South Korean prosecutors said North Korean hackers were behind the so-called denial-of-service attack early this spring, but the North's Ministry of the People's Armed Forces denied it.

No sites in the United States were targeted in this year's attack, but several websites of U.S. military bases in South Korea were hit.

Because of the difficulties in determining the source of the attack, there is no way to declare it an act of war by another country or an act of cyberterrorism, espionage or more basic crime. One problem is that the North's Internet connectivity is difficult to trace because much of it runs through China or Japan.

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