CmdID

CmdID / Rules / Windows

Potential PowerShell Command Line Obfuscation

A Sigma rule for process creation on Windows, by Teymur Kheirkhabarov (idea), Vasiliy Burov (rule), oscd.community, Tim Shelton (fp).

high 2 ATT&CK techniques 3 programs it names

What it looks for

its detection, as SigmaHQ writes it
detection:
  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);'
  selection_img:
    - Image|endswith:
        - '\powershell.exe'
        - '\pwsh.exe'
    - OriginalFileName:
        - 'PowerShell.EXE'
        - 'pwsh.dll'
  selection_re:
    - CommandLine|re: '\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+.*\+'
    - CommandLine|re: '\{.*\{.*\{.*\{.*\{.*\{.*\{.*\{.*\{.*\{'
    - CommandLine|re: '\^.*\^.*\^.*\^.*\^'
    - CommandLine|re: '`.*`.*`.*`.*`'
  condition: all of selection_* and not 1 of filter_optional_*

The rule’s detection, its selections and fields in order of name. The whole rule, with its references and false positives, is on SigmaHQ, by Teymur Kheirkhabarov (idea), Vasiliy Burov (rule), oscd.community, Tim Shelton (fp), under the Detection Rule License 1.1. CmdID evaluates it on a command line alone: a test on what a command line cannot show, such as the parent process or the user, is not met.

None of the everyday examples and documented commands on CmdID’s program pages trips it. To see whether a command line does, paste it into CmdID.

Programs and files it names

their pages here

ATT&CK

the techniques it is tagged with
T1027Obfuscated Files or Information
T1059.001Command and Scripting Interpreter: PowerShell