South Korean police said they had taken a 24-year-old man into custody in connection with the Nth Room, an online sextortion ring that has shocked the nation and driven renewed calls for tougher laws to deal with digital sex crimes.
Three other people, including alleged ringleader Cho Ju-bin, have already been named, and more than 100 people apprehended.
The Nth Room ran on the encrypted messaging service Telegram, and the perpetrators used private information - sometimes collected illegally from local government offices - to blackmail many women and children into performing sexually explicit acts on camera, with thousands of users paying cryptocurrency to watch.