Detection rules › Sigma
Explorer NOUACCHECK Flag
Detects suspicious starts of explorer.exe that use the /NOUACCHECK flag that allows to run all sub processes of that newly started explorer.exe without any UAC checks
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Privilege Escalation | T1548.002 Abuse Elevation Control Mechanism: Bypass User Account Control |
Event coverage
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
Rule body yaml
title: Explorer NOUACCHECK Flag
id: 534f2ef7-e8a2-4433-816d-c91bccde289b
status: test
description: Detects suspicious starts of explorer.exe that use the /NOUACCHECK flag that allows to run all sub processes of that newly started explorer.exe without any UAC checks
references:
- https://twitter.com/ORCA6665/status/1496478087244095491
author: Florian Roth (Nextron Systems)
date: 2022-02-23
modified: 2022-04-21
tags:
- attack.privilege-escalation
- attack.t1548.002
logsource:
category: process_creation
product: windows
detection:
selection:
Image|endswith: '\explorer.exe'
CommandLine|contains: '/NOUACCHECK'
filter_dc_logon:
- ParentCommandLine: 'C:\Windows\system32\svchost.exe -k netsvcs -p -s Schedule'
- ParentImage: 'C:\Windows\System32\svchost.exe' # coarse filter needed for ID 4688 Events
condition: selection and not 1 of filter_*
falsepositives:
- Domain Controller User Logon
- Unknown how many legitimate software products use that method
level: high
Stages and Predicates
Stage 0: condition
selection and not 1 of filter_*Stage 1: selection
selection:
Image|endswith: '\explorer.exe'
CommandLine|contains: '/NOUACCHECK'
Stage 2: not filter_dc_logon
filter_dc_logon:
- ParentCommandLine: 'C:\Windows\system32\svchost.exe -k netsvcs -p -s Schedule'
- ParentImage: 'C:\Windows\System32\svchost.exe'
Exclusions
Top-level NOT(...) conjuncts: predicates this rule actively suppresses.
| Field | Kind | Excluded values |
|---|---|---|
ParentCommandLine | eq | C:\Windows\system32\svchost.exe -k netsvcs -p -s Schedule |
ParentImage | eq | C:\Windows\System32\svchost.exe |
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
CommandLine | match |
|
Image | ends_with |
|