Detect Accessibility Features in Splunk
Adversaries may establish persistence and/or elevate privileges by executing malicious content triggered by accessibility features. Windows has accessibility features that may be launched with a key combination before a user has logged in (for example, when the user is on the Windows logon screen). Adversaries may replace or add code to these programs: sethc.exe (Sticky Keys, invoked with Shift x5), utilman.exe (Utility Manager, Win+U), osk.exe (On-Screen Keyboard), Magnify.exe, Narrator.exe, DisplaySwitch.exe, AtBroker.exe. These programs may be replaced with a command shell (cmd.exe) or backdoor, or the Image File Execution Options (IFEO) debugger key can be used to trigger an arbitrary program instead of the accessibility feature, providing a SYSTEM shell at the logon screen without credentials.
MITRE ATT&CK
- Tactic
- Privilege Escalation Persistence
- Technique
- T1546 Event Triggered Execution
- Sub-technique
- T1546.008 Accessibility Features
- Canonical reference
- https://attack.mitre.org/techniques/T1546/008/
SPL Detection Query
index=wineventlog (sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" OR sourcetype="WinEventLog:Security")
| eval AccessBin=if(
match(lower(coalesce(Image, NewProcessName, "")), "(sethc|utilman|osk|magnify|narrator|displayswitch|atbroker)\.exe"),
1, 0
)
| eval IFEOReg=if(
(EventCode=12 OR EventCode=13)
AND match(TargetObject, "Image File Execution Options")
AND match(lower(TargetObject), "(sethc|utilman|osk|magnify|narrator|displayswitch|atbroker)\.exe")
AND match(lower(TargetObject), "debugger"),
1, 0
)
| eval SysFileMod=if(
EventCode=11
AND match(lower(coalesce(TargetFilename, "")), "(sethc|utilman|osk|magnify|narrator|displayswitch|atbroker)\.exe")
AND match(TargetFilename, "(?i)(system32|syswow64)"),
1, 0
)
| where AccessBin=1 OR IFEOReg=1 OR SysFileMod=1
| eval DetectionType=case(
IFEOReg=1, "IFEO_DEBUGGER_SET",
SysFileMod=1, "SYSTEM_FILE_MODIFIED",
AccessBin=1, "ACCESSIBILITY_BINARY_LAUNCHED",
1=1, "UNKNOWN"
)
| eval Severity=case(
DetectionType="IFEO_DEBUGGER_SET", "CRITICAL",
DetectionType="SYSTEM_FILE_MODIFIED", "CRITICAL",
DetectionType="ACCESSIBILITY_BINARY_LAUNCHED", "HIGH",
1=1, "MEDIUM"
)
| table _time, host, User, EventCode, DetectionType, Severity, TargetObject, Details, Image, CommandLine
| sort - _timeDetects all three accessibility feature abuse vectors: IFEO Debugger key set for accessibility binaries (Sysmon 12/13), direct system file modifications to accessibility binaries (Sysmon 11), and accessibility binary process launches (Sysmon 1). IFEO Debugger modification is rated CRITICAL as it's the primary modern technique — no file replacement needed, just a registry key that redirects execution of any accessibility binary to an arbitrary payload including at the pre-authentication logon screen.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Accessibility software testing
- Assistive technology configuration for users with disabilities
- Remote desktop accessibility feature invocations
- Security testing exercises
Other platforms for T1546.008
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Set IFEO Debugger on sethc.exe (Sticky Keys Backdoor)
Expected signal: Sysmon Event ID 13 (Registry Value Set): TargetObject=HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\sethc.exe\Debugger, Details=C:\Windows\System32\cmd.exe. Security Event ID 4657 if registry auditing is enabled. Process creation for reg.exe.
- Test 2Set IFEO Debugger on utilman.exe (Utility Manager Backdoor)
Expected signal: Sysmon Event ID 13: TargetObject contains Image File Execution Options\utilman.exe\Debugger. Process creation for reg.exe. The combination of IFEO + accessibility binary + Debugger value is a critical detection signal.
- Test 3Scan for Existing Accessibility Feature Backdoors
Expected signal: Process creation for powershell.exe with the enumeration script. Registry read events (Sysmon 12 if monitoring access events) for Image File Execution Options keys. This command is detection-safe — read-only, no modifications.
References (5)
- https://attack.mitre.org/techniques/T1546/008/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1546.008/T1546.008.md
- https://www.fireeye.com/blog/threat-research/2012/08/hikit-rootkit-advanced-persistent-attack.html
- https://blogs.technet.microsoft.com/jonathantrull/2016/10/03/detecting-sticky-key-backdoors/
- https://www.mandiant.com/resources/blog/apt41-dual-espionage-and-cyber-crime-operation
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