The simplicity of the malware that paralyzed the computer networks of three banks and two broadcasters in technically sophisticated South Korea is a warning that U.S. corporations need to rethink security.
The cybercriminals did nothing out of the ordinary in penetrating the organizations' defenses on Wednesday. They used existing malware called "DarkSeoul," changed its signature to evade the organizations' firewalls and antivirus software, and targeted a well-known vulnerability in Internet Explorer (CVE-2012-1889).
"In South Korea, it was a malware that I think, if you say that it took more than one working day to write, it means the developer was not very bright," said Barry Shteiman, a senior security strategist for Imperva.
The malware was capable of infecting Windows, Unix and Linux servers, as well as PCs, Symantec reported on Thursday. Once in the computer, the malware destroyed the master boot record on the hard drive, causing them to crash and unable to turn back on.
As a result, employees at the South Korea's two leading television stations, Korean Broadcasting Systems and MBC, were left staring at blank screens, although normal broadcasts continued, The New York Times reported.
Shinhan Bank, the country's fourth largest, reported its Internet banking servers were temporarily blocked. Two other banks, NongHyup and Jeju, reported computers at some branches were paralyzed for a couple of hours.
What isn't known is how the malware got into the computer systems. Criminals typically send malware in carefully crafted email meant to trick recipients into opening attachments or visiting malicious websites. There's also the possibility that a saboteur installed the malware through a USB drive.
But no matter the method, the criminals were able to bypass the organizations' defensive technology for catching malware before it reached computer systems. In doing so, they were able to wreak havoc using basic technology.
Because no organization's defenses are impenetrable, companies need to think about security as not just stopping an attack from the outside, but uncovering malware once it gets in, experts say. The assumption should be that computer systems are already infected.
With this mindset, companies need to constantly examine hardware and software audit logs to track information that has left the network to look for abnormalities, said James W. Gabberty, a professor of information systems at Pace University. In addition, penetration testing should be performed regularly to catch system vulnerabilities before they are exploited.
Other precautions include identifying where critical data is stored inside a network. In the case of banks, that would mean knowing where the transactional data and customer data is sitting and wrapping it in security technology, so it can't be easily access by malware, Shteiman said.
"You can never fend off all of the mice, but you can make sure the cheese is safe," he said.
The origin of the attackers in the South Korea companies is not known. The country's longtime enemy, North Korea, is a suspect. Other experts say code used in the malware is distinctly Chinese.
Wherever the origin, the attackers were not looking to steal information, but raise havoc, much like the Cyber Fighters of Izz ad-Din al-Qassam, an Islamic group that has launched distributed denial of service (DDoS) attacks in waves against major U.S. banks over the last seven months. Targets included Bank of America, PNC Financial, Capital One Financial, JPMorgan Chase and Citigroup.
While there's no known connection between the attacks, they show how criminals will adopt different strategies, depending on what they want to accomplish. The DDoS attacks on U.S. banks were more advanced technically, but the attackers of the South Korean banks did much more damage.
"At the end of day, the sophistication doesn't particularly matter," said Dan Holden, director of security research at Arbor Networks. "The motivation dictates how sophisticated the attack needs to be."
In the U.S. bank attacks, the motivation appears to be a continuous harassment and constant probing for weaknesses in the bank's online systems. In South Korea, onetime destruction was the goal.
The third wave of attacks against the U.S. bank started again this month after a one-month suspension. In the latest assault, the attackers are constantly changing targets at the application layer of the website, rather than focus on just one for a period of time, Holden said. The format of the bogus data sent to try to overwhelm Web servers is also changing constantly.
In addition, the number of compromised servers spewing data has increased by 50% since the last attacks, Holden said. He declined to give exact numbers.
The banks have managed to fend off the attacks, suffering short periods of downtime at worse. Nevertheless, the attacks have forced the banks to spend more money to defend their systems, Holden said.
The group says the attacks will continue until YouTube removes all versions of an anti-Islam video that mocked the Prophet Muhammad. The video, called the Innocence of Muslims, sparked violent demonstrations last year in many Middle Eastern countries.