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T1546.010 AppInit DLLs

Adversaries may establish persistence and/or elevate privileges by executing malicious content triggered by AppInit DLLs loaded into processes. Dynamic-link libraries (DLLs) that are specified in the AppInit_DLLs value in the Registry keys HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Windows or HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Windows are loaded by user32.dll into every process that loads user32.dll. In practice this is nearly every program, since user32.dll is a very common library. 1

Similar to Process Injection, these values can be abused to obtain elevated privileges by causing a malicious DLL to be loaded and run in the context of separate processes on the computer. 2 Malicious AppInit DLLs may also provide persistence by continuously being triggered by API activity.

The AppInit DLL functionality is disabled in Windows 8 and later versions when secure boot is enabled. 3

Item Value
ID T1546.010
Sub-techniques T1546.001, T1546.002, T1546.003, T1546.004, T1546.005, T1546.006, T1546.007, T1546.008, T1546.009, T1546.010, T1546.011, T1546.012, T1546.013, T1546.014, T1546.015, T1546.016
Tactics TA0004, TA0003
Platforms Windows
Permissions required Administrator
Version 1.1
Created 24 January 2020
Last Modified 21 April 2023

Procedure Examples

ID Name Description
G0087 APT39 APT39 has used malware to set LoadAppInit_DLLs in the Registry key SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows in order to establish persistence.14
S0107 Cherry Picker Some variants of Cherry Picker use AppInit_DLLs to achieve persistence by creating the following Registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows “AppInit_DLLs”=”pserver32.dll”13
S0458 Ramsay Ramsay can insert itself into the address space of other applications using the AppInit DLL Registry key.11
S0098 T9000 If a victim meets certain criteria, T9000 uses the AppInit_DLL functionality to achieve persistence by ensuring that every user mode process that is spawned will load its malicious DLL, ResN32.dll. It does this by creating the following Registry keys: HKLM\Software\Microsoft\Windows NT\CurrentVersion\Windows\AppInit_DLLs – %APPDATA%\Intel\ResN32.dll and HKLM\Software\Microsoft\Windows NT\CurrentVersion\Windows\LoadAppInit_DLLs – 0x1.12

Mitigations

ID Mitigation Description
M1038 Execution Prevention Adversaries can install new AppInit DLLs binaries to execute this technique. Identify and block potentially malicious software executed through AppInit DLLs functionality by using application control 5 tools, like Windows Defender Application Control6, AppLocker, 7 8 or Software Restriction Policies 9 where appropriate. 10
M1051 Update Software Upgrade to Windows 8 or later and enable secure boot.

Detection

ID Data Source Data Component
DS0017 Command Command Execution
DS0011 Module Module Load
DS0009 Process OS API Execution
DS0024 Windows Registry Windows Registry Key Modification

References

  1. Hosseini, A. (2017, July 18). Ten Process Injection Techniques: A Technical Survey Of Common And Trending Process Injection Techniques. Retrieved December 7, 2017. ↩

  2. Microsoft. (2006, October). Working with the AppInit_DLLs registry value. Retrieved July 15, 2015. ↩

  3. Microsoft. (n.d.). AppInit DLLs and Secure Boot. Retrieved July 15, 2015. ↩

  4. Russinovich, M. (2016, January 4). Autoruns for Windows v13.51. Retrieved June 6, 2016. ↩

  5. Beechey, J. (2010, December). Application Whitelisting: Panacea or Propaganda?. Retrieved November 18, 2014. ↩

  6. Gorzelany, A., Hall, J., Poggemeyer, L.. (2019, January 7). Windows Defender Application Control. Retrieved July 16, 2019. ↩

  7. Tomonaga, S. (2016, January 26). Windows Commands Abused by Attackers. Retrieved February 2, 2016. ↩

  8. NSA Information Assurance Directorate. (2014, August). Application Whitelisting Using Microsoft AppLocker. Retrieved March 31, 2016. ↩

  9. Corio, C., & Sayana, D. P. (2008, June). Application Lockdown with Software Restriction Policies. Retrieved November 18, 2014. ↩

  10. Microsoft. (2012, June 27). Using Software Restriction Policies and AppLocker Policies. Retrieved April 7, 2016. ↩

  11. Sanmillan, I.. (2020, May 13). Ramsay: A cyber‑espionage toolkit tailored for air‑gapped networks. Retrieved May 27, 2020. ↩

  12. Grunzweig, J. and Miller-Osborn, J.. (2016, February 4). T9000: Advanced Modular Backdoor Uses Complex Anti-Analysis Techniques. Retrieved April 15, 2016. ↩

  13. Merritt, E.. (2015, November 16). Shining the Spotlight on Cherry Picker PoS Malware. Retrieved April 20, 2016. ↩

  14. FBI. (2020, September 17). Indicators of Compromise Associated with Rana Intelligence Computing, also known as Advanced Persistent Threat 39, Chafer, Cadelspy, Remexi, and ITG07. Retrieved December 10, 2020. ↩