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T1546.008 Accessibility Features

Adversaries may establish persistence and/or elevate privileges by executing malicious content triggered by accessibility features. Windows contains accessibility features that may be launched with a key combination before a user has logged in (ex: when the user is on the Windows logon screen). An adversary can modify the way these programs are launched to get a command prompt or backdoor without logging in to the system.

Two common accessibility programs are C:\Windows\System32\sethc.exe, launched when the shift key is pressed five times and C:\Windows\System32\utilman.exe, launched when the Windows + U key combination is pressed. The sethc.exe program is often referred to as “sticky keys”, and has been used by adversaries for unauthenticated access through a remote desktop login screen. 2

Depending on the version of Windows, an adversary may take advantage of these features in different ways. Common methods used by adversaries include replacing accessibility feature binaries or pointers/references to these binaries in the Registry. In newer versions of Windows, the replaced binary needs to be digitally signed for x64 systems, the binary must reside in %systemdir%\, and it must be protected by Windows File or Resource Protection (WFP/WRP). 3 The Image File Execution Options Injection debugger method was likely discovered as a potential workaround because it does not require the corresponding accessibility feature binary to be replaced.

For simple binary replacement on Windows XP and later as well as and Windows Server 2003/R2 and later, for example, the program (e.g., C:\Windows\System32\utilman.exe) may be replaced with “cmd.exe” (or another program that provides backdoor access). Subsequently, pressing the appropriate key combination at the login screen while sitting at the keyboard or when connected over Remote Desktop Protocol will cause the replaced file to be executed with SYSTEM privileges. 4

Other accessibility features exist that may also be leveraged in a similar fashion: 31

  • On-Screen Keyboard: C:\Windows\System32\osk.exe
  • Magnifier: C:\Windows\System32\Magnify.exe
  • Narrator: C:\Windows\System32\Narrator.exe
  • Display Switcher: C:\Windows\System32\DisplaySwitch.exe
  • App Switcher: C:\Windows\System32\AtBroker.exe
Item Value
ID T1546.008
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
G0016 APT29 APT29 used sticky-keys to obtain unauthenticated, privileged console access.1718
G0022 APT3 APT3 replaces the Sticky Keys binary C:\Windows\System32\sethc.exe for persistence.15
G0096 APT41 APT41 leveraged sticky keys to establish persistence.20
G0001 Axiom Axiom actors have been known to use the Sticky Keys replacement within RDP sessions to obtain persistence.14
G0009 Deep Panda Deep Panda has used the sticky-keys technique to bypass the RDP login screen on remote systems during intrusions.16
S0363 Empire Empire can leverage WMI debugging to remotely replace binaries like sethc.exe, Utilman.exe, and Magnify.exe with cmd.exe.13
G0117 Fox Kitten Fox Kitten has used sticky keys to launch a command prompt.19

Mitigations

ID Mitigation Description
M1038 Execution Prevention Adversaries can replace accessibility features binaries with alternate binaries to execute this technique. Identify and block potentially malicious software executed through accessibility features functionality by using application control 7 tools, like Windows Defender Application Control8, AppLocker, 9 10 or Software Restriction Policies 11 where appropriate. 12
M1035 Limit Access to Resource Over Network If possible, use a Remote Desktop Gateway to manage connections and security configuration of RDP within a network.6
M1028 Operating System Configuration To use this technique remotely, an adversary must use it in conjunction with RDP. Ensure that Network Level Authentication is enabled to force the remote desktop session to authenticate before the session is created and the login screen displayed. It is enabled by default on Windows Vista and later.5

Detection

ID Data Source Data Component
DS0017 Command Command Execution
DS0022 File File Creation
DS0009 Process Process Creation
DS0024 Windows Registry Windows Registry Key Modification

References

  1. Comi, G. (2019, October 19). Abusing Windows 10 Narrator’s ‘Feedback-Hub’ URI for Fileless Persistence. Retrieved April 28, 2020. ↩

  2. Glyer, C., Kazanciyan, R. (2012, August 20). The “Hikit” Rootkit: Advanced and Persistent Attack Techniques (Part 1). Retrieved June 6, 2016. ↩

  3. Maldonado, D., McGuffin, T. (2016, August 6). Sticky Keys to the Kingdom. Retrieved July 5, 2017. ↩↩

  4. Tilbury, C. (2014, August 28). Registry Analysis with CrowdResponse. Retrieved November 12, 2014. ↩

  5. Microsoft. (n.d.). Configure Network Level Authentication for Remote Desktop Services Connections. Retrieved June 6, 2016. ↩

  6. Microsoft. (n.d.). Overview of Remote Desktop Gateway. Retrieved June 6, 2016. ↩

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

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

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

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

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

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

  13. Schroeder, W., Warner, J., Nelson, M. (n.d.). Github PowerShellEmpire. Retrieved April 28, 2016. ↩

  14. Novetta. (n.d.). Operation SMN: Axiom Threat Actor Group Report. Retrieved November 12, 2014. ↩

  15. valsmith. (2012, September 21). More on APTSim. Retrieved September 28, 2017. ↩

  16. RSA Incident Response. (2014, January). RSA Incident Response Emerging Threat Profile: Shell Crew. Retrieved January 14, 2016. ↩

  17. Dunwoody, M. and Carr, N.. (2016, September 27). No Easy Breach DerbyCon 2016. Retrieved October 4, 2016. ↩

  18. Dunwoody, M. (2017, March 27). APT29 Domain Fronting With TOR. Retrieved March 27, 2017. ↩

  19. CISA. (2020, September 15). Iran-Based Threat Actor Exploits VPN Vulnerabilities. Retrieved December 21, 2020. ↩

  20. Fraser, N., et al. (2019, August 7). Double DragonAPT41, a dual espionage and cyber crime operation APT41. Retrieved September 23, 2019. ↩