Privilege Escalation / T1547.004
Winlogon Helper DLL
Sub-technique / Enterprise ATT&CK
Official MITRE entryAdversaries may abuse features of Winlogon to execute DLLs and/or executables when a user logs in. Winlogon.exe is a Windows component responsible for actions at logon/logoff as well as the secure attention sequence (SAS) triggered by Ctrl-Alt-Delete. Registry entries in HKLM\Software[\Wow6432Node\]\Microsoft\Windows NT\CurrentVersion\Winlogon</code> and HKCU\Software\Microsoft\Windows NT\CurrentVersion\Winlogon</code> are used to manage additional helper programs and functionalities that support Winlogon.(Citation: Cylance Reg Persistence Sept 2013)
Malicious modifications to these Registry keys may cause Winlogon to load and execute malicious DLLs and/or executables. Specifically, the following subkeys have been known to be possibly vulnerable to abuse: (Citation: Cylance Reg Persistence Sept 2013)
- Winlogon\Notify - points to notification package DLLs that handle Winlogon events
- Winlogon\Userinit - points to userinit.exe, the user initialization program executed when a user logs on
- Winlogon\Shell - points to explorer.exe, the system shell executed when a user logs on
Adversaries may take advantage of these features to repeatedly execute malicious code and establish persistence.
Parent technique: T1547 Boot or Logon Autostart Execution