Sigma rule: Potential PowerShell Obfuscation Via Reversed Commands

Rule

Title

Potential PowerShell Obfuscation Via Reversed Commands

Status

test

Level

high

Author

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

Date

2020-10-11

Modified

2023-05-31

File

rules/windows/process_creation/proc_creation_win_powershell_cmdline_reversed_strings.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects the presence of reversed PowerShell commands in the CommandLine. This is often used as a method of obfuscation by attackers

Log source

product

windows

category

process_creation

Detection

selection_img:
    - Image|endswith:
          - '\powershell.exe'
          - '\pwsh.exe'
    - OriginalFileName:
          - 'PowerShell.EXE'
          - 'pwsh.dll'
selection_cli:
    CommandLine|contains:
        - 'hctac'
        - 'kaerb'
        - 'dnammoc'
        - 'ekovn' # Also covers 'ekovni'
        - 'eliFd'
        - 'rahc'
        - 'etirw'
        - 'golon'
        - 'tninon'
        - 'eddih'
        - 'tpircS'
        - 'ssecorp'
        - 'llehsrewop'
        - 'esnopser'
        - 'daolnwod'
        - 'tneilCbeW'
        - 'tneilc'
        - 'ptth'
        - 'elifotevas'
        - '46esab'
        - 'htaPpmeTteG'
        - 'tcejbO'
        - 'maerts'
        - 'hcaerof'
        - 'retupmoc'
filter_main_encoded_keyword:
    # We exclude usage of encoded commands as they might generate FPs as shown here:
    #   https://github.com/SigmaHQ/sigma/pull/2720
    #   https://github.com/SigmaHQ/sigma/issues/4270
    CommandLine|contains:
        - ' -EncodedCommand '
        - ' -enc '
condition: all of selection_* and not 1 of filter_main_*

False positives (as the rule lists them)

• Unlikely

Tags

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

MITRE ATT&CK ids this rule names

• T1027
• T1059.001

References

• https://2019.offzone.moscow/ru/report/hunting-for-powershell-abuses/
• https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse?slide=66

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_reversed_strings.yml