Jack Kim reports:
North Korea hacked into more than 140,000 computers at 160 South Korean firms and government agencies, planting malicious code under a long-term plan laying groundwork for a massive cyber attack against its rival, police in the South said on Monday.
South Korea has been on heightened alert against cyber attacks by theNorth after Pyongyang conducted a nuclear test in January and a long-range rocket launch in February that led to new U.N. sanctions.
The North has always denied wrongdoing.
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