Execution via stordiag.exe

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Austin Songer (@austinsonger)
Source: github.com/SigmaHQ/sigma

Detects the use of stordiag.exe to execute schtasks.exe systeminfo.exe and fltmc.exe

Known false positives

Legitimate usage of stordiag.exe.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1218` System Binary Proxy Execution

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: Execution via stordiag.exe
id: 961e0abb-1b1e-4c84-a453-aafe56ad0d34
status: test
description: Detects the use of stordiag.exe to execute schtasks.exe systeminfo.exe and fltmc.exe
references:
    - https://strontic.github.io/xcyclopedia/library/stordiag.exe-1F08FC87C373673944F6A7E8B18CD845.html
    - https://twitter.com/eral4m/status/1451112385041911809
author: Austin Songer (@austinsonger)
date: 2021-10-21
modified: 2022-12-25
tags:
    - attack.stealth
    - attack.t1218
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\stordiag.exe'
        Image|endswith:
            - '\schtasks.exe'
            - '\systeminfo.exe'
            - '\fltmc.exe'
    filter:
        ParentImage|startswith: # as first is "Copy c:\windows\system32\stordiag.exe to a folder"
            - 'c:\windows\system32\'
            - 'c:\windows\syswow64\'
    condition: selection and not filter
falsepositives:
    - Legitimate usage of stordiag.exe.
level: high

Stages and Predicates

Stage 0: `condition`

selection and not filter

Stage 1: `selection`

selection:
    ParentImage|endswith: '\stordiag.exe'
    Image|endswith:
        - '\schtasks.exe'
        - '\systeminfo.exe'
        - '\fltmc.exe'

Stage 2: `not filter`

filter:
    ParentImage|startswith:
        - 'c:\windows\system32\'
        - 'c:\windows\syswow64\'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`ParentImage`	starts_with	`c:\windows\system32\`	`excludes:ParentImage` `field:"ParentImage" value:"c:\windows\system32\"`
`ParentImage`	starts_with	`c:\windows\syswow64\`	`excludes:ParentImage` `field:"ParentImage" value:"c:\windows\syswow64\"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Image`	ends_with	`\fltmc.exe` corpus 3 (sigma 3) `\schtasks.exe` corpus 55 (sigma 55) `\systeminfo.exe` corpus 11 (sigma 11)	`field:"Image" kind:ends_with`
`ParentImage`	ends_with	`\stordiag.exe`	`field:"ParentImage" kind:ends_with value:"\stordiag.exe"`

Execution via stordiag.exe

Known false positives

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: not filter

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter`