February 2018 SSL Threat Report: Zscaler Blog

Zscaler ThreatLabZ's H2 2017 research highlights that growing HTTPS adoption has become a blind spot: encrypted traffic is increasingly used to deliver phishing, exploits, and malware and to host SSL-based C2. The cloud blocked an average of 800,000 malicious SSL transactions per day (a 30% increase), phishing over SSL rose ~300%, and attackers frequently leverage DV/free short-lived certificates and legitimate hosting services to distribute banking trojans, ransomware, and infostealers; the report recommends full SSL inspection as part of a layered defense.