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Potential Modification of Accessibility Binaries

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Potential Modification of Accessibility Binaries

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Windows contains accessibility features that may be launched with a key combination before a user has logged in. An adversary can modify the way these programs are launched to get a command prompt or backdoor without logging in to the system.

Rule type: eql

Rule indices:

winlogbeat-*
logs-endpoint.events.*

Severity: high

Risk score: 73

Runs every: 5 minutes

Searches indices from: now-6m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://www.elastic.co/blog/practical-security-engineering-stateful-detection

Tags:

Elastic
Host
Windows
Threat Detection
Persistence

Version: 6 (version history)

Added (Elastic Stack release): 7.6.0

Last modified (Elastic Stack release): 7.11.2

Rule authors: Elastic

Rule license: Elastic License

Rule query

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process where event.type in ("start", "process_started", "info") and
process.parent.name : ("Utilman.exe", "winlogon.exe") and user.name ==
"SYSTEM" and process.args : (
"C:\\Windows\\System32\\osk.exe",
"C:\\Windows\\System32\\Magnify.exe",
"C:\\Windows\\System32\\Narrator.exe",
"C:\\Windows\\System32\\Sethc.exe", "utilman.exe",
"ATBroker.exe", "DisplaySwitch.exe", "sethc.exe" ) and
not process.pe.original_file_name in ( "osk.exe",
"sethc.exe", "utilman2.exe", "DisplaySwitch.exe",
"ATBroker.exe", "ScreenMagnifier.exe", "SR.exe",
"Narrator.exe", "magnify.exe", "MAGNIFY.EXE" ) /*
uncomment once in winlogbeat to avoid bypass with rogue process with
matching pe original file name */ /* and
process.code_signature.subject_name == "Microsoft Windows" and
process.code_signature.status == "trusted" */

Threat mapping

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Framework: MITRE ATT&CK^TM

Tactic:
- Name: Persistence
- ID: TA0003
- Reference URL: https://attack.mitre.org/tactics/TA0003/
Technique:
- Name: Event Triggered Execution
- ID: T1546
- Reference URL: https://attack.mitre.org/techniques/T1546/
Tactic:
- Name: Privilege Escalation
- ID: TA0004
- Reference URL: https://attack.mitre.org/tactics/TA0004/
Technique:
- Name: Event Triggered Execution
- ID: T1546
- Reference URL: https://attack.mitre.org/techniques/T1546/

Rule version history

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Version 6 (7.11.2 release)

Formatting only

Version 5 (7.11.0 release)

Updated query, changed from:

event.category:process and event.type:(start or process_started) and
process.parent.name:winlogon.exe and not process.name:(atbroker.exe or
displayswitch.exe or magnify.exe or narrator.exe or osk.exe or
sethc.exe or utilman.exe)

Version 4 (7.10.0 release)

Updated query, changed from:

event.code:1 and process.parent.name:winlogon.exe and
process.name:(atbroker.exe or displayswitch.exe or magnify.exe or
narrator.exe or osk.exe or sethc.exe or utilman.exe)

Version 3 (7.9.0 release)

Formatting only

Version 2 (7.7.0 release)

Updated query, changed from:

event.code:1 and process.parent.name:winlogon.exe and
(process.name:atbroker.exe or process.name:displayswitch.exe or
process.name:magnify.exe or process.name:narrator.exe or
process.name:osk.exe or process.name:sethc.exe or
process.name:utilman.exe)

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