Potentially Suspicious Event Viewer Child Process

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Florian Roth (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects uncommon or suspicious child processes of "eventvwr.exe" which might indicate a UAC bypass attempt

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1548.002` Abuse Elevation Control Mechanism: Bypass User Account Control

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Potentially Suspicious Event Viewer Child Process
id: be344333-921d-4c4d-8bb8-e584cf584780
related:
    - id: 7c81fec3-1c1d-43b0-996a-46753041b1b6
      type: derived
status: test
description: Detects uncommon or suspicious child processes of "eventvwr.exe" which might indicate a UAC bypass attempt
references:
    - https://enigma0x3.net/2016/08/15/fileless-uac-bypass-using-eventvwr-exe-and-registry-hijacking/
    - https://www.hybrid-analysis.com/sample/e122bc8bf291f15cab182a5d2d27b8db1e7019e4e96bb5cdbd1dfe7446f3f51f?environmentId=100
author: Florian Roth (Nextron Systems)
date: 2017-03-19
modified: 2023-09-28
tags:
    - attack.privilege-escalation
    - attack.t1548.002
    - car.2019-04-001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\eventvwr.exe'
    filter_main_generic:
        Image|endswith:
            - ':\Windows\System32\mmc.exe'
            - ':\Windows\System32\WerFault.exe'
            - ':\Windows\SysWOW64\WerFault.exe'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_*

Stage 1: `selection`

selection:
    ParentImage|endswith: '\eventvwr.exe'

Stage 2: `not filter_main_generic`

filter_main_generic:
    Image|endswith:
        - ':\Windows\System32\mmc.exe'
        - ':\Windows\System32\WerFault.exe'
        - ':\Windows\SysWOW64\WerFault.exe'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Image`	ends_with	`:\Windows\SysWOW64\WerFault.exe`	`excludes:Image` `field:"Image" value:":\Windows\SysWOW64\WerFault.exe"`
`Image`	ends_with	`:\Windows\System32\WerFault.exe`	`excludes:Image` `field:"Image" value:":\Windows\System32\WerFault.exe"`
`Image`	ends_with	`:\Windows\System32\mmc.exe`	`excludes:Image` `field:"Image" value:":\Windows\System32\mmc.exe"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ParentImage`	ends_with	`\eventvwr.exe` corpus 2 (sigma 2)	`field:"ParentImage" kind:ends_with value:"\eventvwr.exe"`