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Detectionhightest

PowerShell Base64 Encoded IEX Cmdlet

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

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Florian Roth (Nextron Systems)Created Fri Aug 23Updated Thu Apr 0688f680b8-070e-402c-ae11-d2914f2257f1windows
Log Source
WindowsProcess Creation
ProductWindows← raw: windows
CategoryProcess Creation← raw: process_creation

Events generated when a new process is spawned on the system. Covers command-line arguments, parent/child relationships, and process metadata.

Detection Logic
Detection Logic1 selector
detection:
    selection:
        - CommandLine|base64offset|contains:
              - 'IEX (['
              - 'iex (['
              - 'iex (New'
              - 'IEX (New'
              - 'IEX(['
              - 'iex(['
              - 'iex(New'
              - 'IEX(New'
              - "IEX(('"
              - "iex(('"
        # UTF16 LE
        - CommandLine|contains:
              - 'SQBFAFgAIAAoAFsA'
              - 'kARQBYACAAKABbA'
              - 'JAEUAWAAgACgAWw'
              - 'aQBlAHgAIAAoAFsA'
              - 'kAZQB4ACAAKABbA'
              - 'pAGUAeAAgACgAWw'
              - 'aQBlAHgAIAAoAE4AZQB3A'
              - 'kAZQB4ACAAKABOAGUAdw'
              - 'pAGUAeAAgACgATgBlAHcA'
              - 'SQBFAFgAIAAoAE4AZQB3A'
              - 'kARQBYACAAKABOAGUAdw'
              - 'JAEUAWAAgACgATgBlAHcA'
    condition: selection
False Positives
Unknown

False positive likelihood has not been assessed. Additional context may be needed during triage.

References
1
Resolving title…
Internal Research
MITRE ATT&CK
Rule Metadata
Rule ID
88f680b8-070e-402c-ae11-d2914f2257f1
Status
test
Level
high
Type
Detection
Created
Fri Aug 23
Modified
Thu Apr 06
Author
Florian Roth (Nextron Systems)
Path
rules/windows/process_creation/proc_creation_win_powershell_base64_iex.yml
Raw Tags
attack.executionattack.t1059.001
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