NEW : North Korea says hackers often use IP addresses from other countries . Yonhap has staged similar attacks in the past , expert says . It has threatened to attack its neighbor with nuclear weapons and has also threatened the United States . Previous attacks linked to the South have been traced to South Koreans addresses . Banks , broadcasters targeted ; government networks unaffected , North Korea reports .
NEW : North Korea says hackers often use IP addresses from other countries . Yonhap has staged similar attacks in the past , expert says . Previous attacks linked to the South have been traced to South Koreans addresses . Banks , broadcasters targeted ; government networks unaffected , North Korea reports .