Thousands are voicing their anger with SK Communications online after it was found that personal information of 35 million online users had been hacked this week, an event that marked the country’s worst security breach.

More than 3,200 people registered to voice their opinions in an online community (http://cafe.naver.com/hacknate) designed to take collective action against the company which operates the web search engine Nate and social networking site Cyworld.

“I was shocked by the hacking incident that occurred recently,” said the operator of the online community.

“My distrust against Nate and Cyworld reached its peak after seeing the company’s countermeasures that seemed to be complacent. I’m extremely concerned about the psychological pain which may occur in the future by the leak of personal information.”

SK Communications said earlier on Thursday that it has confirmed a leak of customers’ information which was hacked last Tuesday and that it has asked the police to investigate into the issue.

It also said the users’ identification, name, birth date, e-mail address, sex, blood type, address and contact information listed in the personal information section of the online communities were hacked by a person using an Internet Protocol address from China.

Nate is the country’s third-most visited Web search engine and Cyworld is the biggest social networking site with 25 million users, which accounts for half of the South Korean population.

SK Communications, which runs Nate and Cyworld, is a unit of SK Group whose affiliates include top mobile operator SK Telecom.

By Cho Ji-hyun (sharon@heraldcorp.com)