The attacks that disrupted operations at several South Korean banks, broadcast companies and energy firms have technical similarities that may link the digital campaign to a series of DDoS (distributed denial-of-service) attacks in 2011, security firm Symantec stated in a blog post on March 29.
On March 4, 2011, more than three dozen South Korean Websites became the focus of a sophisticated distributed denial-of-service attack that caused outages for 10 days and then—following an internal timer—switched tactics to destroying data on any infected machines.
In addition to the data-wiping tactic, both attacks used a variant of a program, known as Backdoor.Prioxer, to allow the attackers access to compromised computers. The malware from the 2011 campaign and the malware in the latest campaign, known as Jokra, both used the same packer to scramble the binary code in an effort to make it unrecognizable to antivirus software, Symantec stated.
Finally, and perhaps most intriguingly, both programs appear to have been developed from source code stored in the same directory or path: "Z:\Work\Make Troy\".
"The 'work' path is peculiar because it could mean that someone was hired to do this attack," Satnam Narang, security response manager with Symantec, told eWEEK. "We don't know for sure, but that is a peculiar thing to see."
On March 19, security firms reported that attackers had infected systems at Korean broadcasters, banks and at least one energy firm with malware that deleted data and made the compromised systems unusable. The attacks reportedly caused network outages at the Korea Broadcasting System, Yonhap News Network, Shinhan Bank and the Korea Gas Corp., which network monitoring firm Renesys confirmed in a March 20 blog post.
The attack involved at least four different variants of the Jokra wiper program, including one that checked for remote Linux systems and uploaded a script to delete files on those systems as well, according to Symantec.
Researchers typically attempt to link attacks based on a set of qualities known as techniques, tactics and procedures (TTPs), clustering attacks that use the same methods or have similar technical characteristics. Yet, matching attributes fall well short of proving that a link exists between attacks.
"It is certainly suspicious that versions of Backdoor.Prioxer have been present during both attacks, but it could be explained away as the Trojan merely being discovered during the course of an investigation and not actually being related to the attacks," Symantec stated in its blog post. "However, we think it is likely that the samples are related, given the Jokra connection."
Suspicions for the attack quickly fell on North Korea, which had blamed South Korea and its ally, the United States, for taking its networks offline for two days the week of March 11.
South Korean officials pledged to work with the United States to further develop their capabilities to defend and operate in cyberspace, according to an article published by the Korean news agency Yonhap on April 1. South Korea has a cyber-command unit consisting of about 400 security professionals, while North Korea allegedly has its own unit consisting of 4,000 hackers, the news agency stated.