Symantec has uncovered digital evidence that links cyber-attacks on South Korea dating back four years to a hacking group dubbed the "Dark Seoul Gang".
Eric Chien, technical director with Symantec Security Response, found the connection while looking under the bonnet of malicious software code used to launch attacks that disrupted some South Korean government websites earlier in the week.
While Symantec could not place the identity of the gang members, researchers found chunks of code that were identical to code in malicious programs used in four previous significant attacks, the first of which happened on July 4, 2009, according to Chien.
South Korean has blamed the North for some of the attacks. Pyongyang denies responsibility and has said it has also been a victim. Symantec said that regardless of whether the gang is working on behalf of North Korea or not, the attacks are both politically motivated and have the necessary financial support to continue acts of cybersabotage on organisations in South Korea.
Chien said that it is clear they are one gang, but are extremely well coordinated.
He thinks that the group has between 10 and 50 members, based on the sophistication of the code and the complexity of their attacks.
These included a 4 July, 2009, attack which wiped data on PCs and also launched distributed denial of service attacks that disrupted websites in South Korea as well as the United States.
In March of this year, the gang knocked tens of thousands of PCs offline at South Korean companies by destroying data on their hard drives, Chien said.
This was one of the most destructive cyber attacks on private computer networks to date.
The most recent attack, Tuesday, the anniversary of the start of the Korean War in 1950, brought down the main websites of South Korea's presidential office and some local newspapers.