A teenage hacker and an operator of a Telegram chatroom in his 20s were arrested on the charge of leaking scores of 270,000 high school sophomores of a mock scholastic ability test held nationwide in November last year, the police said Thursday.

The 19-year-old has allegedly broke into the Gyeonggi Office of Education‘s server on Feb. 18 and stole the mock test results of high school sophomores, according to Gyeonggi Nambu Provincial Police Agency. The teenager gave the data to the Telegram chatroom operator who later distributed at his chatroom which had about 18,000 participants.

The teen hacker is also accused of using overseas IP addresses 200 times for five months since October last year, to break into the education office‘s server. He downloaded several pieces of data about 100 times, according to investigators.

The education office was completely unaware of the damage during the five months the teen was constantly hacking the server.

The teen hacker told investigators that he was curious about his test grades and found a vulnerability of the server by chance. He confessed to transferring the data to a Telegram chatroom to show off his skills.

In a separate case in April, police caught seven others, including three suspects who illegally hacked the education office's server for test scores, three suspects who distributed the hacked data, and one suspect who tried to sell the data. Their cases have been sent to the prosecution without taking them into custody.