The notorious North Korean cyber syndicate Kimsuky is suspected of taking control of a North Korean defector’s messenger account earlier this year to send malicious files to her contacts, South Korean police said Thursday.

According to a national security cyber investigation official from the Gyeonggi Nambu Provincial Police Agency, the cybercriminals sent the messages in September from Kim Eun-ju’s KakaoTalk account to more than 30 of her contacts.

Each message included a file and a note reading, “This file contains stress-relief methods, please open it.”

Kim, who escaped from North Korea and now works for the Canada-based nonprofit HanVoice,