Tracking Down Hackers With Passive DNS Data and SSL Certificates

In early February 2018, Bui Thanh Hieu received an email. It was an invitation to an event he had been planning to attend. Bui Thanh Hieu, a Vietnamese dissident and blogger, living in Germany, knows he needs to be cautious. He nevertheless clicked the link in the email. It didn't look suspicious and seemed to come from a familiar email address.