Epson Korea Co., the South Korean unit of Japan's Seiko Epson Corp., said Saturday that its Web site has been hacked, causing the private information of 35 million users to be leaked. "We have discovered through an internal investigation that the customers' data were leaked. We apologize for causing the trouble," said Epson Korea in a pop-up notice on its Web site. The company said that it had detected the security breach a week ago but reported the cyber attack to the Korea Communications Commission (KCC) belatedly on Thursday. The company said that it has put more priority on informing its customers of the hacking. Personal information leaked included names, user IDs, passwords and resident registration numbers, according to the company. Epson Korea said it is trying to track the hackers but has found no trace of them. Epson Korea said that it has asked its customers to change their passwords on its Web sites and other portal sites. Two popular Web sites operated by SK Communications Co. were hacked in late July, causing the private information of 35 million users to be leaked. A local court earlier this week ordered the operator of South Korea's third most-visited Internet portal to pay a victim 1 million won (US$925) in compensation.