South Korean authorities have arrested two hackers accused of stealing the residential registration numbers of some 8.7 million mobile subscribers, a security vendor reported Tuesday.

In a blog post, BitDefender cited an Agence France Presse report that the two targeted KT, the second biggest mobile phone operator in South Korea.

“We deeply bow our head in apology for having your precious personal information leaked… we’ll try our best to make such things never happen again,” BitDefender quoted KT as  saying in statement after the incident.

Citing the AFP report, BitDefender said KT reported the breach to police on July 13, but the taking of customers’ data may have already been taking place for five months at the time.

It cited a separate report by Korea’s Yonhap news agency indicating one of the attackers used to work for a local IT company as a senior programmer.

He may have made at least $800,000 by selling the stolen data to telemarketing operators, the report added.

“The number of affected people account for nearly a half of about 17 million customers of ours,” a KT spokesman was quoted as telling AFP.

BitDefender noted that in July 2011, hackers attacked web portal Nate.com and social network Cyworld, both owned by SK Communications.

In that incident, the hackers allegedly accessed the personal data of more than 35 million users. In November 2011, Nexon Korea online gamers were hacked and 13.2 million subscribers’ personal data were leaked. — LBG, GMA News