Some of the malicious software used in the cyberattack that recently shut down tens of thousands of computers across South Korea originated in the United States and three European countries, the Washington Times reports, citing authorities in Seoul.
The cyberattack last week crippled six South Korean banks and media companies.
"We traced some IP (Internet protocol) addresses found on (affected) computer networks to overseas sources like the U.S. and a few European countries," an official from the Korean Communications Commission purportedly said Monday.
Many first suspected North Korea was responsible for the attack, but South Korean officials have yet to assign blame and say they have no proof yet of North Korea's involvement.
South Korea has set up a team of computer security experts from the government, military and private sector to identify the hackers and is preparing to deal with more possible attacks, presidential spokesman Yoon Chang-jung told reporters Friday. He didn't elaborate on the possibility of more attacks, but he said the prime minister later would hold a meeting to discuss ways to beef up cybersecurity at institutions overseeing infrastructure such as roads and electricity.
The cyberattack did not affect South Korea's government, military or infrastructure, and there were no initial reports that customers' bank records were compromised. But it disabled cash machines and disrupted commerce in this tech-savvy, Internet-dependent country, renewing questions about South Korea's Internet security and vulnerability to hackers.
The attack disabled some 32,000 computers at broadcasters YTN, MBC and KBS, as well as three banks. The broadcasters said their programming was never affected.
All three of the banks that were hit were back online and operating regularly Friday. It could be next week before the media companies have fully recovered.
The Associated Press contributed to this report.