Cyberattackers have attacked South Korean banks and broadcasters, infecting networks with a malicious program that slowed or shut systems down.

South Korea's military stepped up its cyberdefense efforts in response to the widespread outages, which hit nine companies, Yonhap reported, citing the National Police Agency. Government computer networks did not seem to be affected, said CNN.

While the source of the problem remained unclear, a South Korean official close to the investigation told CNN that malicious computer code spread through hacking caused the outages.

How the hackers got in and spread the code remains under investigation, and analysts are examining the malware, CNN said.

McAfee’s Phyllis Schneck, chief technology officer, Global Public Sector at McAfee, told Security magazine:

 “As we see more cyber espionage and targeted attacks,the need for enhanced layered defense that reaches below the OS to the device hardware is even more critical. McAfee and Intel have developed hardware enhanced technology that stops MBR rootkits before they have a chance to take control of devices, spread, and change operations. Cyber attacks harm the largest entities to the smallest, and the good news is with hardware assist and a smart, connected security investment, we can truly change the game against these types of acts and begin to lower the profit model for those that cause the harm."