Yoon’s office said the cyberattack only affected the personal account of the unidentified employee, who violated security protocols by partially using commercial email services to handle official duties. Officials did not specify what type of information was stolen from the staff member’s personal emails but stressed that the office’s overall security system was not affected.

“We detected the case in advance of (Yoon’s) visit and took necessary measures,” Yoon’s office said in a statement to reporters. The office said it has been monitoring and defending against “constant” hacking attempts presumed to be related to North Korea but “it’s not that the presidential office’s security system got hacked.”