Execution of Powershell Script in Public Folder

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

This rule detects execution of PowerShell scripts located in the "C:\Users\Public" folder

Known false positives

Unlikely

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059.001` Command and Scripting Interpreter: PowerShell

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 of Powershell Script in Public Folder
id: fb9d3ff7-7348-46ab-af8c-b55f5fbf39b4
status: test
description: This rule detects execution of PowerShell scripts located in the "C:\Users\Public" folder
references:
    - https://www.mandiant.com/resources/evolution-of-fin7
author: Max Altgelt (Nextron Systems)
date: 2022-04-06
modified: 2022-07-14
tags:
    - attack.execution
    - attack.t1059.001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\powershell.exe'
            - '\pwsh.exe'
        CommandLine|contains:
            - '-f C:\Users\Public'
            - '-f "C:\Users\Public'
            - '-f %Public%'
            - '-fi C:\Users\Public'
            - '-fi "C:\Users\Public'
            - '-fi %Public%'
            - '-fil C:\Users\Public'
            - '-fil "C:\Users\Public'
            - '-fil %Public%'
            - '-file C:\Users\Public'
            - '-file "C:\Users\Public'
            - '-file %Public%'
    condition: selection
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith:
        - '\powershell.exe'
        - '\pwsh.exe'
    CommandLine|contains:
        - '-f C:\Users\Public'
        - '-f "C:\Users\Public'
        - '-f %Public%'
        - '-fi C:\Users\Public'
        - '-fi "C:\Users\Public'
        - '-fi %Public%'
        - '-fil C:\Users\Public'
        - '-fil "C:\Users\Public'
        - '-fil %Public%'
        - '-file C:\Users\Public'
        - '-file "C:\Users\Public'
        - '-file %Public%'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`-f "C:\Users\Public` `-f %Public%` `-f C:\Users\Public` `-fi "C:\Users\Public` `-fi %Public%` `-fi C:\Users\Public` `-fil "C:\Users\Public` `-fil %Public%` `-fil C:\Users\Public` `-file "C:\Users\Public` `-file %Public%` `-file C:\Users\Public`	`field:"CommandLine" kind:match`
`Image`	ends_with	`\powershell.exe` corpus 179 (sigma 178, kusto 1) `\pwsh.exe` corpus 165 (sigma 164, kusto 1)	`field:"Image" kind:ends_with`

Execution of Powershell Script in Public Folder

Known false positives

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`