Sigma rule: Malicious Base64 Encoded PowerShell Keywords in Command Lines

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-6c45c017d79b, updated 2023-01-05T00:00:00.000Z.

Rule

Title
Malicious Base64 Encoded PowerShell Keywords in Command Lines
Status
test
Level
high
Author
John Lambert (rule)
Date
2019-01-16
Modified
2023-01-05
File
rules/windows/process_creation/proc_creation_win_powershell_base64_hidden_flag.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects base64 encoded strings used in hidden malicious PowerShell command lines

Log source

product
windows
category
process_creation

Detection

selection_img:
    - Image|endswith:
          - '\powershell.exe'
          - '\pwsh.exe'
    - OriginalFileName:
          - 'PowerShell.EXE'
          - 'pwsh.dll'
selection_hidden:
    CommandLine|contains: ' hidden '
selection_encoded:
    CommandLine|contains:
        - 'AGkAdABzAGEAZABtAGkAbgAgAC8AdAByAGEAbgBzAGYAZQByA'
        - 'aXRzYWRtaW4gL3RyYW5zZmVy'
        - 'IAaQB0AHMAYQBkAG0AaQBuACAALwB0AHIAYQBuAHMAZgBlAHIA'
        - 'JpdHNhZG1pbiAvdHJhbnNmZX'
        - 'YgBpAHQAcwBhAGQAbQBpAG4AIAAvAHQAcgBhAG4AcwBmAGUAcg'
        - 'Yml0c2FkbWluIC90cmFuc2Zlc'
        - 'AGMAaAB1AG4AawBfAHMAaQB6AGUA'
        - 'JABjAGgAdQBuAGsAXwBzAGkAegBlA'
        - 'JGNodW5rX3Npem'
        - 'QAYwBoAHUAbgBrAF8AcwBpAHoAZQ'
        - 'RjaHVua19zaXpl'
        - 'Y2h1bmtfc2l6Z'
        - 'AE8ALgBDAG8AbQBwAHIAZQBzAHMAaQBvAG4A'
        - 'kATwAuAEMAbwBtAHAAcgBlAHMAcwBpAG8Abg'
        - 'lPLkNvbXByZXNzaW9u'
        - 'SQBPAC4AQwBvAG0AcAByAGUAcwBzAGkAbwBuA'
        - 'SU8uQ29tcHJlc3Npb2'
        - 'Ty5Db21wcmVzc2lvb'
        - 'AE8ALgBNAGUAbQBvAHIAeQBTAHQAcgBlAGEAbQ'
        - 'kATwAuAE0AZQBtAG8AcgB5AFMAdAByAGUAYQBtA'
        - 'lPLk1lbW9yeVN0cmVhb'
        - 'SQBPAC4ATQBlAG0AbwByAHkAUwB0AHIAZQBhAG0A'
        - 'SU8uTWVtb3J5U3RyZWFt'
        - 'Ty5NZW1vcnlTdHJlYW'
        - '4ARwBlAHQAQwBoAHUAbgBrA'
        - '5HZXRDaHVua'
        - 'AEcAZQB0AEMAaAB1AG4Aaw'
        - 'LgBHAGUAdABDAGgAdQBuAGsA'
        - 'LkdldENodW5r'
        - 'R2V0Q2h1bm'
        - 'AEgAUgBFAEEARABfAEkATgBGAE8ANgA0A'
        - 'QASABSAEUAQQBEAF8ASQBOAEYATwA2ADQA'
        - 'RIUkVBRF9JTkZPNj'
        - 'SFJFQURfSU5GTzY0'
        - 'VABIAFIARQBBAEQAXwBJAE4ARgBPADYANA'
        - 'VEhSRUFEX0lORk82N'
        - 'AHIAZQBhAHQAZQBSAGUAbQBvAHQAZQBUAGgAcgBlAGEAZA'
        - 'cmVhdGVSZW1vdGVUaHJlYW'
        - 'MAcgBlAGEAdABlAFIAZQBtAG8AdABlAFQAaAByAGUAYQBkA'
        - 'NyZWF0ZVJlbW90ZVRocmVhZ'
        - 'Q3JlYXRlUmVtb3RlVGhyZWFk'
        - 'QwByAGUAYQB0AGUAUgBlAG0AbwB0AGUAVABoAHIAZQBhAGQA'
        - '0AZQBtAG0AbwB2AGUA'
        - '1lbW1vdm'
        - 'AGUAbQBtAG8AdgBlA'
        - 'bQBlAG0AbQBvAHYAZQ'
        - 'bWVtbW92Z'
        - 'ZW1tb3Zl'
condition: all of selection_*

False positives (as the rule lists them)

  • Unknown

Tags

  • attack.execution
  • attack.t1059.001

MITRE ATT&CK ids this rule names

References

  • http://www.leeholmes.com/blog/2017/09/21/searching-for-content-in-base-64-strings/

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_base64_hidden_flag.yml

Sources and licences

  • SigmaHQ

    "Malicious Base64 Encoded PowerShell Keywords in Command Lines" by John Lambert (rule) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_powershell_base64_hidden_flag.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: Malicious Base64 Encoded PowerShell Keywords in Command Lines",
entity page, dataset version ref-6c45c017d79b, updated 2023-01-05T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/f26c6093-6f14-4b12-800f-0fcb46f5ffd0 (accessed 2026-11-03).
Underlying source: SigmaHQ rule f26c6093-6f14-4b12-800f-0fcb46f5ffd0, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.