As part of our commitment to keeping our customers/community protected & informed, we are releasing a blog that shines light on transition between Stage 1 and 2 of #Solorigate/#SUNBURST campaign, custom Cobalt Strike loaders, post-exploit. artifacts, IOCs: https://t.co/b0ReHMa63u

Here are some highlights:
The missing link between the Solorigate backdoor and the custom #CobaltStrike loaders observed during the #Solorigate is an Image File Execution Options (IFEO) Debugger registry value created for the legitimate process dllhost.exe (ATT&CK ID: T1546.012).

Once the registry value is created, the attackers wait for the occasional execution of dllhost.exe, which might happen naturally on a system. This execution triggers a process launch of wscript.exe configured to run the VBScript file dropped by the SolarWinds backdoor (Stage 1).

The VBScript in turn runs rundll32.exe, activating the Cobalt Strike loader DLL using a clean parent/child process tree completely disconnected from the SolarWinds process. Finally, the VBScript removes the previously created IFEO value to clean up any traces of execution.

On the custom Cobalt Strike Loaders: we identified several second-stage malware, including TEARDROP, Raindrop, and other custom loaders for the Cobalt Strike beacon. During the lateral movement phase, the custom loader DLLs are dropped mostly in existing Windows sub-directories.