Bkis, as a member of APCERT, received a request from KrCERT (Korean Computer Emergency Response Team) to investigate the incident that was performing DDoS attacks on websites of South Korea and the US.

We have analyzed the malware pattern that we received from KrCERT and have located the botnet controlled by 8 Command and Control (C&C) servers via controlling code embedded in a file named "flash.gif". Every 3 minutes, zombies randomly select one of the 8 servers to connect to and to receive orders. Especially, we found a master server located in UK which controls all of the 8 C&C servers to make a series of cyber-attack last week. So the source of the attacks has been identified to be in UK. The existence of master server has never been reported before.

ddos attack diagram

In order to locate the source of the attacks, we have fought against C&C servers and have gained control of 2 in 8 of them. After analyzing the logs of these 2 servers, we discovered the IP address of the master server, which is 195.90.118.xxx. This IP is located in UK. The master server is running on Windows 2003 Server Operating System..

Blog IP attack
© Blog IP attack
During the past few days, the number of zombies has been estimated to be 50,000 by Symantec and about 20,000 by Government of South Korea. But, by taking control of two C&C servers and analyzing logs on these servers, we count the exact number of zombies that have been querying C&C servers to receive commands. Accordingly, there have been 166,908 zombies from 74 countries around the world that have been used for the attacks.

Top 10 zombies host countries

No. Country
1 Korea, Republic of
3 United States
4 China
5 Canada
6 Australia
7 Philippines
8 New Zealand
9 United Kingdom
10 Vietnam

Having located the attacking source in UK, we believed that it is completely possible to find out the hacker. This of course depends on the US and South Korean governments. We have sent KrCERT and US-CERT the IP address of the attacking source.

Bkis has sent the detail of research and the information of the master server in UK to US-CERT and KrCERT.

At present, US-CERT and KrCERT are cooperating to investigate the attack source.

The Korea Communications Commission (KCC) also confirmed of the Bkis report. "The Korea Communications Commission (KCC), the country's broadcasting and telecommunications regulator, backed Bkis report and said law enforcement authorities are currently seeking cooperation with the British government to investigate the attack source".

Nguyen Minh Duc is the Senior Security Researcher / Bkis Security Director