Sigma rule: Potential PowerShell Command Line Obfuscation

Rule

Title

Potential PowerShell Command Line Obfuscation

Status

test

Level

high

Author

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

Date

2020-10-15

Modified

2024-04-15

File

rules/windows/process_creation/proc_creation_win_powershell_cmdline_special_characters.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects the PowerShell command lines with special characters

Log source

product

windows

category

process_creation

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_*

False positives (as the rule lists them)

• Amazon SSM Document Worker
• Windows Defender ATP

Tags

• attack.execution
• attack.stealth
• attack.t1027
• attack.t1059.001

MITRE ATT&CK ids this rule names

• T1027
• T1059.001

References

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

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_powershell_cmdline_special_characters.yml