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Detection rules › Sigma

Suspicious Get-Variable.exe Creation

Status
test
Severity
high
Log source
product windows, category file_event
Author
frack113
Source
github.com/SigmaHQ/sigma

Get-Variable is a valid PowerShell cmdlet WindowsApps is by default in the path where PowerShell is executed. So when the Get-Variable command is issued on PowerShell execution, the system first looks for the Get-Variable executable in the path and executes the malicious binary instead of looking for the PowerShell cmdlet.

MITRE ATT&CK coverage

TacticTechniques
PersistenceT1546 Event Triggered Execution
Privilege EscalationT1546 Event Triggered Execution
StealthT1027 Obfuscated Files or Information

Event coverage

ProviderEventTitle
SysmonEvent ID 11FileCreate

Rule body yaml

title: Suspicious Get-Variable.exe Creation
id: 0c3fac91-5627-46e8-a6a8-a0d7b9b8ae1b
status: test
description: |
    Get-Variable is a valid PowerShell cmdlet
    WindowsApps is by default in the path where PowerShell is executed.
    So when the Get-Variable command is issued on PowerShell execution, the system first looks for the Get-Variable executable in the path and executes the malicious binary instead of looking for the PowerShell cmdlet.
references:
    - https://blog.malwarebytes.com/threat-intelligence/2022/04/colibri-loader-combines-task-scheduler-and-powershell-in-clever-persistence-technique/
    - https://www.joesandbox.com/analysis/465533/0/html
author: frack113
date: 2022-04-23
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.stealth
    - attack.t1546
    - attack.t1027
logsource:
    product: windows
    category: file_event
detection:
    selection:
        TargetFilename|endswith: 'Local\Microsoft\WindowsApps\Get-Variable.exe'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    TargetFilename|endswith: 'Local\Microsoft\WindowsApps\Get-Variable.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.

FieldKindValues
TargetFilenameends_with
  • Local\Microsoft\WindowsApps\Get-Variable.exe