This will go down as one of the world’s biggest hacks. A South Korea social networking site, Cyworld, has had the account details of 35 million users stolen — that is almost two thirds of the South Korean population.

The site was hit along  with the Nate portal, both run by SK Telecom, in an attack being blame on Chinese hackers.

The hackers are thought to have stolen names, addresses, phone numbers, emails and other encrypted information in a huge haul according to the Korea Communications Commission. The population of South Korea is 48.7  million.

Reuters reports that South Korean police are investigating the cyberattack, which follows a series of hacking incidents on South Korean financial firms in recent months.

In April the government-backed bank, Nonghyup, was hit and a month later data on more than 1.8 million customers was stolen from Hyundai Capital, which is owned by Hyundai Motor and GE Capital International.

Cyworld is a South Korean Facebook type social networking site. The “Cy” in Cyworld as well as meaning “cyber” is also a pun on the Korean word for relationship.

CyWorld generates revenue via the sale of dotori or “acorns”, which can then be used to purchase virtual goods such as background music, pixelated furniture and virtual appliances. CyWorld also operates in China and Vietnam.

While the attack is large it is still less than half of that stolen when hackers hit Sony’s Playstation Network and its music and video on-demand service, Qriocity, earlier this year. That attack in mid-April may have netted hackers the details of more than 100 million accounts.