sigmahighHunting

Potential PowerShell Command Line Obfuscation

Detects the PowerShell command lines with special characters

MITRE ATT&CK

executiondefense-evasion

Detection Query

selection_img:
  - Image|endswith:
      - \powershell.exe
      - \pwsh.exe
  - OriginalFileName:
      - PowerShell.EXE
      - pwsh.dll
selection_re:
  - CommandLine|re: \+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+
  - CommandLine|re: \{.*\{.*\{.*\{.*\{.*\{.*\{.*\{.*\{.*\{
  - CommandLine|re: \^.*\^.*\^.*\^.*\^
  - CommandLine|re: "`.*`.*`.*`.*`"
filter_optional_amazonSSM:
  ParentImage: C:\Program Files\Amazon\SSM\ssm-document-worker.exe
filter_optional_defender_atp:
  CommandLine|contains:
    - new EventSource("Microsoft.Windows.Sense.Client.Management"
    - public static extern bool InstallELAMCertificateInfo(SafeFileHandle
      handle);
condition: all of selection_* and not 1 of filter_optional_*

Author

Teymur Kheirkhabarov (idea), Vasiliy Burov (rule), oscd.community, Tim Shelton (fp)

Created

2020-10-15

Data Sources

windowsProcess Creation Events

Platforms

windows

References

https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse?slide=64

Tags

attack.executionattack.defense-evasionattack.t1027attack.t1059.001

Raw Content

title: Potential PowerShell Command Line Obfuscation
id: d7bcd677-645d-4691-a8d4-7a5602b780d1
status: test
description: Detects the PowerShell command lines with special characters
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse?slide=64
author: Teymur Kheirkhabarov (idea), Vasiliy Burov (rule), oscd.community, Tim Shelton (fp)
date: 2020-10-15
modified: 2024-04-15
tags:
    - attack.execution
    - attack.defense-evasion
    - attack.t1027
    - attack.t1059.001
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\powershell.exe'
              - '\pwsh.exe'
        - OriginalFileName:
              - 'PowerShell.EXE'
              - 'pwsh.dll'
    selection_re:
        # TODO: Optimize for PySIGMA
        - CommandLine|re: '\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+'
        - CommandLine|re: '\{.*\{.*\{.*\{.*\{.*\{.*\{.*\{.*\{.*\{'
        - CommandLine|re: '\^.*\^.*\^.*\^.*\^'
        - CommandLine|re: '`.*`.*`.*`.*`'
    filter_optional_amazonSSM:
        ParentImage: C:\Program Files\Amazon\SSM\ssm-document-worker.exe
    filter_optional_defender_atp:
        CommandLine|contains:
            - 'new EventSource("Microsoft.Windows.Sense.Client.Management"'
            - 'public static extern bool InstallELAMCertificateInfo(SafeFileHandle handle);'
    condition: all of selection_* and not 1 of filter_optional_*
falsepositives:
    - Amazon SSM Document Worker
    - Windows Defender ATP
level: high