PowerShell Base64 Encoded IEX Cmdlet

 1title: PowerShell Base64 Encoded IEX Cmdlet
 2id: 88f680b8-070e-402c-ae11-d2914f2257f1
 3status: test
 4description: Detects usage of a base64 encoded "IEX" cmdlet in a process command line
 5references:
 6    - Internal Research
 7author: Florian Roth (Nextron Systems)
 8date: 2019/08/23
 9modified: 2023/04/06
10tags:
11    - attack.execution
12    - attack.t1059.001
13logsource:
14    category: process_creation
15    product: windows
16detection:
17    selection:
18        - CommandLine|base64offset|contains:
19              - 'IEX (['
20              - 'iex (['
21              - 'iex (New'
22              - 'IEX (New'
23              - 'IEX(['
24              - 'iex(['
25              - 'iex(New'
26              - 'IEX(New'
27              - "IEX(('"
28              - "iex(('"
29        # UTF16 LE
30        - CommandLine|contains:
31              - 'SQBFAFgAIAAoAFsA'
32              - 'kARQBYACAAKABbA'
33              - 'JAEUAWAAgACgAWw'
34              - 'aQBlAHgAIAAoAFsA'
35              - 'kAZQB4ACAAKABbA'
36              - 'pAGUAeAAgACgAWw'
37              - 'aQBlAHgAIAAoAE4AZQB3A'
38              - 'kAZQB4ACAAKABOAGUAdw'
39              - 'pAGUAeAAgACgATgBlAHcA'
40              - 'SQBFAFgAIAAoAE4AZQB3A'
41              - 'kARQBYACAAKABOAGUAdw'
42              - 'JAEUAWAAgACgATgBlAHcA'
43    condition: selection
44falsepositives:
45    - Unknown
46level: high