A Vietnamese computer security firm believes Britain was the likely origin of last week's cyber attacks that crippled major US and South Korean websites, South Korean officials told Agence France-Presse.

The Korea Communications Commission said the information came from Vietnamese firm Bach Khoa Internetwork Security.

Vietnam is part of a regional grouping known as the Asia Pacific Computer Emergency Response Team.

"The (British) server appears to have controlled compromised handler servers" which spread viruses, said Park Cheol-Soon, a network protection team leader of the government-run communications commission.

"However, it needs more investigation to confirm whether this server was the final attacker server or not," he told AFP.

Seoul's National Intelligence Service earlier said North Korea was a prime suspect in the attacks, which briefly crippled major government and commercial websites in the United States and South Korea.

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