South Korean authorities have found that a man arrested on suspicion of brokering prostitution had developed and sold an app that enables brothel owners to filter out calls from undercover policemen.

According to the Seoul Metropolitan Police Agency on Wednesday, the 40-year-old man surnamed Choi, who was once a bar employee, got the idea from apps that filter out spam calls and had an unidentified app professional create it for 3.5 million won ($3,106) in July 2015.


According to the police, the app, named Golden Bell, identifies whether the caller is a guest or a police officer based on information shared by its users.
Brothel operators who were busted by undercover policemen provide the phone numbers of the officers to the app’s database to help other business operators avoid crackdowns. The database had about 5 million phone numbers of guests and policemen collected this way, police said.

It also showed information about callers with unregistered number by retrieving data from internet and social media such as Facebook, Google and Naver.

Choi sold the app to 448 sex workers nationwide for a monthly fee of 50,000 won. The money he earned through it from Nov. 4, 2015, to March 13 amounts to 120 million won.

“Prostitution is evolving into a high-tech crime,” a police official said. “I was surprised to see all the phone numbers I use in the office entered into the app.”

Along with Kim, police arrested 44 others on suspicion of offenses related to the illegal sex trade, including 17 Thai prostitutes and 21 brothel staff.

By Byun Hee-jin (hjbandi9@heraldcorp.com)