South Korea Computer Crash
Depositors leave after checking their accounts through automated teller machines of Shinhan Bank at a subway station as the bank's computer networks ...
Depositors leave after checking their accounts through automated teller machines of Shinhan Bank at a subway station as the bank's computer networks was paralyzed in Seoul, South Korea, Wednesday, March 20, 2013. Police and South Korean officials were investigating the simultaneous shutdown Wednesday of computer networks at several major broadcasters and banks. While the cause wasn't immediately clear, speculation centered on a possible North Korean cyberattack. (AP Photo/Ahn Young-joon)
South Korea Computer Crash
Employees of Korea Internet Security Center work after computer networks at two major South Korean banks and three top TV broadcasters went into shut...
Employees of Korea Internet Security Center work after computer networks at two major South Korean banks and three top TV broadcasters went into shutdown mode en masse, at a monitoring room in Seoul, South Korea, Wednesday, March 20, 2013. Police and South Korean officials investigating the shutdown said the cause was not immediately clear. But speculation centered on North Korea, with experts saying a cyberattack orchestrated by Pyongyang was likely to blame. (AP Photo/Yonhap, Han Jong-chan) Korea Out
APTOPIX South Korea Computer Crash
Two bank clerks, left, check an automated teller machine at a branch of Shinhan Bank after the bank's computer networks are fixed in Seoul, South Kor...
Two bank clerks, left, check an automated teller machine at a branch of Shinhan Bank after the bank's computer networks are fixed in Seoul, South Korea, Wednesday, March 20, 2013. Computers networks at two major South Korean banks and three top TV broadcasters went into shutdown mode en masse Wednesday, paralyzing bank machines across the country and prompting speculation of a cyberattack by North Korea. (AP Photo/Lee Jin-man)
APTOPIX South Korea Computer Crash
Depositors try to use automated teller machines of Shinhan Bank while the bank's computer networks are paralyzed at a subway station in Seoul, South ...
Depositors try to use automated teller machines of Shinhan Bank while the bank's computer networks are paralyzed at a subway station in Seoul, South Korea, Wednesday, March 20, 2013. Computer networks at two major South Korean banks and three top TV broadcasters went into shutdown mode en masse Wednesday, paralyzing bank machines across the country and prompting speculation of a cyberattack by North Korea. (AP Photo/Ahn Young-joon)
APTOPIX South Korea Computer Crash
A depositor leaves after checking his account through an automated teller machine at a subway station as the bank's computer networks was paralyzed i...
A depositor leaves after checking his account through an automated teller machine at a subway station as the bank's computer networks was paralyzed in Seoul, South Korea, Wednesday, March 20, 2013. Police and South Korean officials were investigating the simultaneous shutdown Wednesday of computer networks at several major broadcasters and banks. While the cause wasn't immediately clear, speculation centered on a possible North Korean cyberattack. (AP Photo/Ahn Young-joon)
South Korea Computer Crash
Visitors look at North Korea through binoculars a day after a cyberattack caused networks at major South Korean banks and top TV broadcasters to cras...
Visitors look at North Korea through binoculars a day after a cyberattack caused networks at major South Korean banks and top TV broadcasters to crash simultaneously, at the Unification Observation Post at in Paju near the demilitarized zone between the two Koreas, South Korea,Thursday, March 21, 2013. It�s too early to assign blame - Internet addresses can easily be manipulated and the investigation could take weeks - but suspicion for Wednesday�s shutdown quickly fell on North Korea, which has threatened Seoul and Washington with attack in recent days because of anger over U.N. sanctions imposed for its Feb. 12 nuclear test. (AP Photo/Ahn Young-joon)
South Korea Computer Crash
South Korean computer researchers, left, check the shutdown computer serves of Korean Broadcasting System (KBS) as a South Korean police officer from...
South Korean computer researchers, left, check the shutdown computer serves of Korean Broadcasting System (KBS) as a South Korean police officer from Digital Forensic Investigation looks on at Cyber Terror Response Center at National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese Internet address was the source of a cyberattack on one company hit in a massive network shutdown that affected 32,000 computers at six banks and media companies in South Korea, initial findings indicated Thursday. (AP Photo/Lee Jin-man)
South Korea Computer Crash
A man walks past next to a sign of Cyber Terror Response Center at National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese ...
A man walks past next to a sign of Cyber Terror Response Center at National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese Internet address was the source of a cyberattack on one company hit in a massive network shutdown that affected 32,000 computers at six banks and media companies in South Korea, initial findings indicated Thursday. (AP Photo/Lee Jin-man)
South Korea Computer Crash
A South Korean police officer from Digital Forensic Investigation, center, tries to enter the Cyber Terror Response Center as members of media wait a...
A South Korean police officer from Digital Forensic Investigation, center, tries to enter the Cyber Terror Response Center as members of media wait at National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese Internet address was the source of a cyberattack on one company hit in a massive network shutdown that affected 32,000 computers at six banks and media companies in South Korea, initial findings indicated Thursday. (AP Photo/Lee Jin-man)
South Korea Computer Crash
Members of media are reflected on the door of Cyber Terror Response Center as they wait to enter the lab at National Police Agency in Seoul, South Ko...
Members of media are reflected on the door of Cyber Terror Response Center as they wait to enter the lab at National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese Internet address was the source of a cyberattack on one company hit in a massive network shutdown that affected 32,000 computers at six banks and media companies in South Korea, initial findings indicated Thursday. (AP Photo/Lee Jin-man)
South Korea Computer Crash
Two South Korean computer researchers look at the computer monitors as they check the shutdown computer servers of Korean Broadcasting System (KBS) a...
Two South Korean computer researchers look at the computer monitors as they check the shutdown computer servers of Korean Broadcasting System (KBS) at Cyber Terror Response Center at National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese Internet address was the source of a cyberattack on one company hit in a massive network shutdown that affected 32,000 computers at six banks and media companies in South Korea, initial findings indicated Thursday. (AP Photo/Lee Jin-man)
South Korea Computer Crash
A South Korean computer researcher checks the shutdown computer servers of Korean Broadcasting System (KBS) at Cyber Terror Response Center at Nation...
A South Korean computer researcher checks the shutdown computer servers of Korean Broadcasting System (KBS) at Cyber Terror Response Center at National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese Internet address was the source of a cyberattack on one company hit in a massive network shutdown that affected 32,000 computers at six banks and media companies in South Korea, initial findings indicated Thursday. (AP Photo/Lee Jin-man)
South Korea Computer Crash
Visitors look at North Korea through binoculars a day after a cyberattack caused networks at major South Korean banks and top TV broadcasters to cras...
Visitors look at North Korea through binoculars a day after a cyberattack caused networks at major South Korean banks and top TV broadcasters to crash simultaneously, at the Unification Observation Post at in Paju near the demilitarized zone between the two Koreas, South Korea,Thursday, March 21, 2013. It�s too early to assign blame - Internet addresses can easily be manipulated and the investigation could take weeks - but suspicion for Wednesday�s shutdown quickly fell on North Korea, which has threatened Seoul and Washington with attack in recent days because of anger over U.N. sanctions imposed for its Feb. 12 nuclear test. (AP Photo/Ahn Young-joon)
South Korea Computer Crash
A man walks past near the signs of Cyber Terror Response Center at National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese ...
A man walks past near the signs of Cyber Terror Response Center at National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese Internet address was the source of a cyberattack on one company hit in a massive network shutdown that affected 32,000 computers at six banks and media companies in South Korea, initial findings indicated Thursday. (AP Photo/Lee Jin-man)
South Korea Computer Crash
A South Korean computer researcher looks at a computer monitor as he checks the shutdown computer servers of Korean Broadcasting System (KBS) at Evid...
A South Korean computer researcher looks at a computer monitor as he checks the shutdown computer servers of Korean Broadcasting System (KBS) at Evidence Acquisition Lab of Cyber Terror Response Center at National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese Internet address was the source of a cyberattack on one company hit in a massive network shutdown that affected 32,000 computers at six banks and media companies in South Korea, initial findings indicated Thursday. (AP Photo/Lee Jin-man)
South Korea Computer Crash
Unidentified men arrive at Cyber Terror Response Center of National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese Internet...
Unidentified men arrive at Cyber Terror Response Center of National Police Agency in Seoul, South Korea, Thursday, March 21, 2013. A Chinese Internet address was the source of a cyberattack on one company hit in a massive network shutdown that affected 32,000 computers at six banks and media companies in South Korea, initial findings indicated Thursday. (AP Photo/Lee Jin-man)
A Chinese Internet address was the source of a cyberattack on one of the South Korean companies hit in a massive computer shutdown that affected five other banks or media companies, initial findings indicated Thursday.
It's too early to assign blame _ Internet addresses can easily be manipulated and disguised _ but suspicion for Wednesday's shutdown quickly fell on North Korea, which has threatened Seoul with attack in recent days because of anger over U.N. sanctions imposed for its Feb. 12 nuclear test.
Experts say hackers often attack via computers in other countries to hide their identities. South Korea has previously accused North Korean hackers of using Chinese addresses to attack.
The crash Wednesday caused computer networks at major banks and top TV broadcasters to crash simultaneously. It paralyzed bank machines across the country and raised fears that this heavily Internet-dependent society was vulnerable.
A Chinese address created the malicious code in the server of one of the banks, Nonghyup, where computers crashed, according to an initial analysis by the state-run Korea Communications Commission, South Korea's telecom regulator.
It is expected to take at least four to five days for the infected computers to recover fully.
Regulators have distributed vaccine software to government offices, banks, hospitals and other institutions to prevent more outages.
