North Korea behind March cyber attack, says South Korea

Investigation discovers hack can be traced back to North Korea

North Korea was responsible for a cyber attack which last month shut down tens of thousands of computers across South Korea, officials in Seoul have said.

South Korea's internet security agency revealed that an internal investigation has discovered that a military-based spy agency was responsible for the attacks on a television network and disrupted banks. It comes at a time when tensions between the two nations are extremely high.

The agency points to six computers in North Korea using more than 1,000 overseas-based IP addresses to launch the attack, which a spokesman said had been planned for about eight months.

"We saw evidence that the attack was extremely carefully prepared," said Chun Kil-soo, an official at South Korea's internet security agency.

Investigators discovered similarities between the March cyber attack and previous hacking incidents attributed to North Korea. These include the re-use of 30 previously used elements of malware among the 76 programs used to make the attack.

The cyber attack on South Korea, which took place on 20 March, affected almost 50,000 computers and services, affecting television news channels and causing problems for South Korean banks for almost five days, although no personal details are said to have been compromised. The attack didn't appear to target government, military or infrastructure.

Nonetheless, Lim Chae-ho, professor of network security at the Korea Advanced Institute of Science and Technology, warned about what might come in future.

"It is worrisome that the North's cyber attacks are getting increasingly severe," he said.

Cyber crime appears to be becoming an increasingly used tool for political point-scoring between states, with both China and the US accusing one another of being responsible for attacks.

The US has also warned of the threats posed by Iranian cyber warriors.