Of note, we also discovered the Sofacy group using a very similar delivery document to deliver a new Trojan called Cannon. Cannon uses SMTPS and POP3S as its C2 channel compared to Zebrocy that uses a more commonly observed HTTP or HTTPS based C2. Add the layer of encryption that the SMTPS and POP3S protocols provide to the legitimate web-based service and you have a very difficult C2 channel to block