Massive North Korea cyber attack thwarted after hacking South Korea - report

A man types on a computer keyboard in Warsaw in this February 28, 2013 illustration file picture. REUTERS/Kacper Pempel/Files

SEOUL (Reuters) - 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 the North after Pyongyang conducted a nuclear test in January and a long-range rocket launch in February that led to new U.N. sanctions.