The personal information of about 35 million internet users in South Korea was stolen in an alleged hacking attack that originated in China, officials said Thursday.
Hackers purportedly attacked popular internet and social media sites Nate and Cyworld earlier this week, stealing data such as social security numbers and email addresses, the Korea Communications Commission said in a statement.
The regulator said that the operator of the sites, SK Communications, alleged the attack originated from computers in China based on their Internet Protocol addresses. IP addresses are the Web equivalent of a street address or phone number.
The stolen data included user IDs, passwords, social security numbers, names, mobile phone numbers and email addresses. Nate said the social security numbers and passwords are encrypted so that they are not available for illegal use.
South Korean police said Thursday their investigation could take several months.
Kim Jie-won, a KCC official, said that if proven, the alleged attack would be the largest internet hacking case to have taken place in South Korea.
The country is one of the most wired in the world and its citizens some of the most internet-savvy. South Korea has a population of about 50 million people. More than 80 per cent of households have broadband access to the internet, according to the country's statistical office.
South Korea has faced internet attacks before, with blame frequently pinned on hackers operating from IP addresses in China. China has denied all charges of hacking in the past and says the country itself is a victim of hacking.
In May, South Korean prosecutors said that hackers in North Korea had broken into the computer network of a South Korean bank earlier this year. The prosecutors said software used in the hacking was similar to that used in a 2009 attack that paralysed South Korean and US websites.
North Korea has flatly denied any responsibility for the attacks.