South Korean police are investigating one of the country's biggest Internet shutdowns for evidence of a North Korean cyberattack, after simultaneous outages Wednesday paralyzed computer systems at major television networks and banks for several hours.
Servers at three TV stations, a number of commercial banks, including Shinhan Bank and Nonghyup, and two insurance companies were either shut down or severely disrupted from around 2 p.m. local time, police and government officials said. Some systems were still down in late evening.
Government and military sites were unaffected by the attack, but the military raised its information surveillance status.
Television broadcasts continued throughout the outages and bank branches remained open, although some retail- and business-banking services were inaccessible to staff. Banks said automated teller and Internet banking operations were affected.
Speculation immediately focused on North Korea. South Korea's communication watchdog said the attacks were caused by malicious code, but it didn't have any evidence linking the attack to North Korea. There were reports of skulls appearing on the screens of affected computers.
North Korean state media made no comment on the incident. Investigations into hacking attacks can take weeks or months.
"We're looking into the cause of the shutdown, but we can't say North Korea is behind it," said a spokesperson for South Korea's president. Police also said it was too early to pin the blame on the North.
LG Uplus, an internet service provider for two of the broadcasters affected, KBS and YTN, said a hacking attack was likely but its own networks continued to function normally.
Seoul has said North Korea has been behind a series of cyberattacks in recent years, including malware incidents and " denial-of-service" attacks that inundate websites with requests for information, causing them to crash. In the previous attacks the network of a local bank crashed in April 2011, while the website of a major newspaper was brought down in June 2012. A number of government websites were attacked in July 2009.
The South Korean government believes at least some North Korean hackers are based in China