Consider hiring a Security Engineer for future issues. As for the current issue, are you a target for any known reason. Is their anything of value on the server

Consider hiring a Security Engineer for future issues. As for the current issue, are you a target for any known reason. Is their anything of value on the server? If not, it's highly possible someone in your group who already has access could be involved. Otherwise, maybe the Security Engineer serendipitously found you.