In April, FireEye Managed Defense (or Mandiant) detected and described intrusion by FIN6 threat actor and their latest tactics, techniques, and procedures (TTPs). In particular, they used also LockerGoga and Ryuk ransomware families, and Cobalt Strike for initial compromise and lateral movement. Even three months after publishing their post, some of the URLs for Cobalt Strike stagers have been still active, so I decided to publish analysis of these Cobalt Strike stagers and payloads.
Introduction In the first part of this analysis have been presented the two types of macro-enabled documents with powershell downloader spreading via emails in recent campaign. The powershell downloaders and/or the macros were slightly obfuscated, however, it was easy to defeat this obfuscation and reveal their purpose. Unfortunately, during my analysis the downloaded content was not present on the involved servers and also in the most cases it was not available even during the analysis on sandboxes like Any.
Overview During the first half of February 2019 there was an increase in occurrences of the Spam messages containing attached documents with the names in the form “Request” followed by the number, like “Request15.doc”. These documents contain slightly obfuscated macros which lead to execution of the PowerShell downloader. This PowerShell downloader connects to the domains registered in Russian Federation and resolved to the Russian IP addresses. It seems that on these servers are hosted malicious content, in many cases detected as the Ursnif malware.