To steal the data, the hackers allegedly uploaded malicious code onto posts on online forums, which provided them with access to the relevant sites when site admins clicked on them.
The three allegedly sold the stolen data to customers including loan providers and chauffeur companies for 100 million Won, or $93,475.
Two of the alleged hackers, surnamed Kim and Choi, are 21 years old, while the third, named Lee, is 18. Kim was previously arrested in 2012 for spreading malware on online forums.
According to the police, the three started stealing the data in September of 2013 from organizations including the Korean Medical Association, the Association of Korean Medicine and the Korean Dental Association, along with stock market, real estate, and online gambling sites.
Lee apparently told the police that he was initially involved only in the sale of stolen data, but soon got involved with hacking as well.
"I just gave it a try and it was very easy," he said.
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