Rundll32

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Rundll32
Technique
ID T1085
Tactic Defense Evasion, Execution
Platform Windows Server 2003, Windows Server 2003 R2, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2, Windows XP, Windows Vista, Windows 7, Windows 8, Windows 8.1
Permissions Required User
Data Sources File monitoring, Binary file metadata, Process command-line parameters, Process monitoring
Supports Remote No
Defense Bypassed Process whitelisting, Anti-virus

The rundll32.exe program can be called to execute an arbitrary binary. Adversaries may take advantage of this functionality to proxy execution of code to avoid triggering security tools that may not monitor execution of the rundll32.exe process because of whitelists or false positives from Windows using rundll32.exe for normal operations.

Examples

  • APT28 executed CHOPSTICK by using rundll32 commands such as rundll32.exe “C:\Windows\twain_64.dll”.1
  • Carbanak installs VNC server software that executes through rundll32.2
  • JHUHUGIT is executed using rundll32.exe.3
  • The CozyCar dropper copies the system file rundll32.exe to the install location for the malware, then uses the copy of rundll32.exe to load and execute the main CozyCar component.4
  • Sakula calls cmd.exe to run various DLL files via rundll32.5
  • After copying itself to a DLL file, a variant of Elise calls the DLL file using rundll32.exe.6
  • Variants of Emissary have used rundll32.exe in Registry values added to establish persistence.7
  • Prikormka uses rundll32.exe to load its DLL.8
  • PowerDuke uses rundll32.exe to load.9

Detection

Use process monitoring to monitor the execution and arguments of rundll32.exe. Compare recent invocations of rundll32.exe with prior history of known good arguments and loaded DLLs to determine anomalous and potentially adversarial activity. Command arguments used with the rundll32.exe invocation may also be useful in determining the origin and purpose of the DLL being loaded.