Sigma rule: PowerShell Base64 Encoded FromBase64String Cmdlet

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-85d647e2652f, updated 2023-04-06T00:00:00.000Z.

Rule

Title
PowerShell Base64 Encoded FromBase64String Cmdlet
Status
test
Level
high
Author
Florian Roth (Nextron Systems)
Date
2019-08-24
Modified
2023-04-06
File
rules/windows/process_creation/proc_creation_win_powershell_base64_frombase64string.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects usage of a base64 encoded "FromBase64String" cmdlet in a process command line

Log source

product
windows
category
process_creation

Detection

selection:
    - CommandLine|base64offset|contains: '::FromBase64String'
    # UTF-16 LE
    - CommandLine|contains:
          - 'OgA6AEYAcgBvAG0AQgBhAHMAZQA2ADQAUwB0AHIAaQBuAGcA'
          - 'oAOgBGAHIAbwBtAEIAYQBzAGUANgA0AFMAdAByAGkAbgBnA'
          - '6ADoARgByAG8AbQBCAGEAcwBlADYANABTAHQAcgBpAG4AZw'
condition: selection

False positives (as the rule lists them)

  • Unknown

Tags

  • attack.stealth
  • attack.t1140
  • attack.execution
  • attack.t1059.001

MITRE ATT&CK ids this rule names

References

  • Internal Research

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_frombase64string.yml

Sources and licences

  • SigmaHQ

    "PowerShell Base64 Encoded FromBase64String Cmdlet" by Florian Roth (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_powershell_base64_frombase64string.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: PowerShell Base64 Encoded FromBase64String Cmdlet",
entity page, dataset version ref-85d647e2652f, updated 2023-04-06T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/fdb62a13-9a81-4e5c-a38f-ea93a16f6d7c (accessed 2026-11-03).
Underlying source: SigmaHQ rule fdb62a13-9a81-4e5c-a38f-ea93a16f6d7c, 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.