309. Adversaries Use Hidden Hyper-V Virtual Machines

Hello everyone!

Using virtual machines for defense evasion becomes more and more popular. Today we'll look at another example of Hide Artifacts: Run Virtual Instance (T1564.006).

According to the report, the adversary enabled the Hyper-V feature on a compromised Windows machine, then downloaded and imported a lightweight Alpine Linux-based VM containing their malware.

Once downloaded, the virtual machine was imported using PowerShell:

"cmd.exe" /C powershell.exe -c import-vm -path "c:\\programdata\\microsoft\\AppV\\app\\Virtual Machines\\1DBCC80B-5803-4AF1-8772-712C688F408A.vmcx" -Copy -GenerateNewId > c:\\Programdata\\WindowsUpdateTask_t.tmp 2>&1

PowerShell was also used to start the newly imported virtual machine:

"cmd.exe" /C powershell.exe -c Start-VM -name WSL > c:\\Programdata\\WindowsUpdateTask_R.tmp 2>&1

For example, we can hunt for cmdlets related to virtual machine manipulation:

event_type: "processcreatewin"

AND

proc_file_path: "powershell.exe"

AND

cmdline: ("import-vm" OR "start-vm")

See you tomorrow!

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