North Korea's General Bureau of Reconnaissance repeatedly collected information from South Korea's weather agency before the North torpedoed the Navy corvette Cheonan in March 2010.
A Unification Ministry report from 2011 revealed Thursday said hackers from the bureau accessed the website of the Korea Meteorological Administration about 300 times the previous year to browse satellite photos and thermal images, apparently to assist them in planning the attack.
An official involved in compiling the report said it was drawn up based on the data provided by the National Intelligence Service. "The time period of North's constant accessing of the website was just before the attack on the Cheonan," he said. "The hackers routed IP addresses through countries in Africa and Central America to bypass security firewalls."
The bureau's hackers have been responsible for a string of cyber attacks and wiretapping of communication networks.
On this occasion, they seemed to be gathering data about the tidal currents, speeds and directions of flow around Baeknyeong Island from the KMA website the better to plan the attack.
