By Kim Rahn

The perpetrator of the massive cyber attack on websites of government agencies and financial institutions last month was North Korea, police said Wednesday.

The National Police Agency's Cyber Terror Response Center said the distributed denial of service (DDos) attack from March 3 to 5 mimicked the attack in July 2009, which was confirmed to have been orchestrated by the North.

"We analyzed the websites spreading malicious codes, 'zombie' computers here and foreign servers making the attack and concluded that the two attacks were the same in terms of the attack system, method, malicious code programming and many more aspects. We believe the same programmers were involved," an official of the center said.

In 2009, the attack was made from 435 servers in 61 countries on 35 major government and financial bodies in South Korea and the U.S. between July 7 and 9.

Police confirmed at the time that the attack came from an Internet protocol (IP) address based in China used by the North Korean Ministry of Post and Telecommunications.

"Some foreign servers used in the 2009 attack were used again last month. There are more than 4.2 billion IP addresses across the world: it is almost impossible to use the same IP addresses in the two attacks unless they were made by the same user," he said.

The official said it seems the North had prepared for seven months before implementing the attack.

"Such massive, long-term planning can't be made by several individual hackers. The attack also targeted government websites. Considering these, we concluded it was systematic and intentional cyber terrorrism by North Korea," he said.

The March attack spread malicious codes and infected about 100,000 computers. Then the "zombie" computers were used to carry out DDos attacks by receiving orders from 746 servers in 70 countries, according to police.

"We'll trace more causes of the attacks and foreign servers through cooperation with foreign law enforcement authorities. We'll also request related agencies to prepare more protective measures against DDos attacks, such as strengthening fire walls," the official said.