Net WebClient Casing Anomalies

calendar Nov 2, 2023 · attack.execution attack.t1059.001  ·
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Detects PowerShell command line contents that include a suspicious abnormal casing in the Net.Webclient (e.g. nEt.WEbCliEnT) string as used in obfuscation techniques

Sigma rule (View on GitHub)

  1title: Net WebClient Casing Anomalies
  2id: c86133ad-4725-4bd0-8170-210788e0a7ba
  3status: test
  4description: Detects PowerShell command line contents that include a suspicious abnormal casing in the Net.Webclient (e.g. nEt.WEbCliEnT) string as used in obfuscation techniques
  5references:
  6    - https://app.any.run/tasks/b9040c63-c140-479b-ad59-f1bb56ce7a97/
  7author: Florian Roth (Nextron Systems)
  8date: 2022/05/24
  9modified: 2023/01/05
 10tags:
 11    - attack.execution
 12    - attack.t1059.001
 13logsource:
 14    category: process_creation
 15    product: windows
 16detection:
 17    selection_img:
 18        - Image|endswith:
 19              - '\powershell.exe'
 20              - '\pwsh.exe'
 21        - OriginalFileName:
 22              - 'PowerShell.EXE'
 23              - 'pwsh.dll'
 24    selection_encoded:
 25        CommandLine|contains:
 26            - 'TgBlAFQALgB3AEUAQg'
 27            - '4AZQBUAC4AdwBFAEIA'
 28            - 'OAGUAVAAuAHcARQBCA'
 29            - 'bgBFAHQALgB3AGUAYg'
 30            - '4ARQB0AC4AdwBlAGIA'
 31            - 'uAEUAdAAuAHcAZQBiA'
 32            - 'TgBFAHQALgB3AGUAYg'
 33            - 'OAEUAdAAuAHcAZQBiA'
 34            - 'bgBlAFQALgB3AGUAYg'
 35            - '4AZQBUAC4AdwBlAGIA'
 36            - 'uAGUAVAAuAHcAZQBiA'
 37            - 'TgBlAFQALgB3AGUAYg'
 38            - 'OAGUAVAAuAHcAZQBiA'
 39            - 'bgBFAFQALgB3AGUAYg'
 40            - '4ARQBUAC4AdwBlAGIA'
 41            - 'uAEUAVAAuAHcAZQBiA'
 42            - 'bgBlAHQALgBXAGUAYg'
 43            - '4AZQB0AC4AVwBlAGIA'
 44            - 'uAGUAdAAuAFcAZQBiA'
 45            - 'bgBFAHQALgBXAGUAYg'
 46            - '4ARQB0AC4AVwBlAGIA'
 47            - 'uAEUAdAAuAFcAZQBiA'
 48            - 'TgBFAHQALgBXAGUAYg'
 49            - 'OAEUAdAAuAFcAZQBiA'
 50            - 'bgBlAFQALgBXAGUAYg'
 51            - '4AZQBUAC4AVwBlAGIA'
 52            - 'uAGUAVAAuAFcAZQBiA'
 53            - 'TgBlAFQALgBXAGUAYg'
 54            - 'OAGUAVAAuAFcAZQBiA'
 55            - 'bgBFAFQALgBXAGUAYg'
 56            - '4ARQBUAC4AVwBlAGIA'
 57            - 'uAEUAVAAuAFcAZQBiA'
 58            - 'bgBlAHQALgB3AEUAYg'
 59            - '4AZQB0AC4AdwBFAGIA'
 60            - 'uAGUAdAAuAHcARQBiA'
 61            - 'TgBlAHQALgB3AEUAYg'
 62            - 'OAGUAdAAuAHcARQBiA'
 63            - 'bgBFAHQALgB3AEUAYg'
 64            - '4ARQB0AC4AdwBFAGIA'
 65            - 'uAEUAdAAuAHcARQBiA'
 66            - 'TgBFAHQALgB3AEUAYg'
 67            - 'OAEUAdAAuAHcARQBiA'
 68            - 'bgBlAFQALgB3AEUAYg'
 69            - '4AZQBUAC4AdwBFAGIA'
 70            - 'uAGUAVAAuAHcARQBiA'
 71            - 'TgBlAFQALgB3AEUAYg'
 72            - 'OAGUAVAAuAHcARQBiA'
 73            - 'bgBFAFQALgB3AEUAYg'
 74            - '4ARQBUAC4AdwBFAGIA'
 75            - 'uAEUAVAAuAHcARQBiA'
 76            - 'TgBFAFQALgB3AEUAYg'
 77            - 'OAEUAVAAuAHcARQBiA'
 78            - 'bgBlAHQALgBXAEUAYg'
 79            - '4AZQB0AC4AVwBFAGIA'
 80            - 'uAGUAdAAuAFcARQBiA'
 81            - 'TgBlAHQALgBXAEUAYg'
 82            - 'OAGUAdAAuAFcARQBiA'
 83            - 'bgBFAHQALgBXAEUAYg'
 84            - '4ARQB0AC4AVwBFAGIA'
 85            - 'uAEUAdAAuAFcARQBiA'
 86            - 'TgBFAHQALgBXAEUAYg'
 87            - 'OAEUAdAAuAFcARQBiA'
 88            - 'bgBlAFQALgBXAEUAYg'
 89            - '4AZQBUAC4AVwBFAGIA'
 90            - 'uAGUAVAAuAFcARQBiA'
 91            - 'TgBlAFQALgBXAEUAYg'
 92            - 'OAGUAVAAuAFcARQBiA'
 93            - 'bgBFAFQALgBXAEUAYg'
 94            - '4ARQBUAC4AVwBFAGIA'
 95            - 'uAEUAVAAuAFcARQBiA'
 96            - 'TgBFAFQALgBXAEUAYg'
 97            - 'OAEUAVAAuAFcARQBiA'
 98            - 'bgBlAHQALgB3AGUAQg'
 99            - '4AZQB0AC4AdwBlAEIA'
100            - 'uAGUAdAAuAHcAZQBCA'
101            - 'TgBlAHQALgB3AGUAQg'
102            - 'OAGUAdAAuAHcAZQBCA'
103            - 'bgBFAHQALgB3AGUAQg'
104            - '4ARQB0AC4AdwBlAEIA'
105            - 'uAEUAdAAuAHcAZQBCA'
106            - 'TgBFAHQALgB3AGUAQg'
107            - 'OAEUAdAAuAHcAZQBCA'
108            - 'bgBlAFQALgB3AGUAQg'
109            - '4AZQBUAC4AdwBlAEIA'
110            - 'uAGUAVAAuAHcAZQBCA'
111            - 'TgBlAFQALgB3AGUAQg'
112            - 'OAGUAVAAuAHcAZQBCA'
113            - 'bgBFAFQALgB3AGUAQg'
114            - '4ARQBUAC4AdwBlAEIA'
115            - 'uAEUAVAAuAHcAZQBCA'
116            - 'TgBFAFQALgB3AGUAQg'
117            - 'OAEUAVAAuAHcAZQBCA'
118            - 'bgBlAHQALgBXAGUAQg'
119            - '4AZQB0AC4AVwBlAEIA'
120            - 'uAGUAdAAuAFcAZQBCA'
121            - 'TgBlAHQALgBXAGUAQg'
122            - 'OAGUAdAAuAFcAZQBCA'
123            - 'bgBFAHQALgBXAGUAQg'
124            - '4ARQB0AC4AVwBlAEIA'
125            - 'uAEUAdAAuAFcAZQBCA'
126            - 'TgBFAHQALgBXAGUAQg'
127            - 'OAEUAdAAuAFcAZQBCA'
128            - 'bgBlAFQALgBXAGUAQg'
129            - '4AZQBUAC4AVwBlAEIA'
130            - 'uAGUAVAAuAFcAZQBCA'
131            - 'TgBlAFQALgBXAGUAQg'
132            - 'OAGUAVAAuAFcAZQBCA'
133            - 'bgBFAFQALgBXAGUAQg'
134            - '4ARQBUAC4AVwBlAEIA'
135            - 'uAEUAVAAuAFcAZQBCA'
136            - 'TgBFAFQALgBXAGUAQg'
137            - 'OAEUAVAAuAFcAZQBCA'
138            - 'bgBlAHQALgB3AEUAQg'
139            - '4AZQB0AC4AdwBFAEIA'
140            - 'uAGUAdAAuAHcARQBCA'
141            - 'TgBlAHQALgB3AEUAQg'
142            - 'OAGUAdAAuAHcARQBCA'
143            - 'bgBFAHQALgB3AEUAQg'
144            - '4ARQB0AC4AdwBFAEIA'
145            - 'uAEUAdAAuAHcARQBCA'
146            - 'TgBFAHQALgB3AEUAQg'
147            - 'OAEUAdAAuAHcARQBCA'
148            - 'bgBlAFQALgB3AEUAQg'
149            - 'uAGUAVAAuAHcARQBCA'
150            - 'bgBFAFQALgB3AEUAQg'
151            - '4ARQBUAC4AdwBFAEIA'
152            - 'uAEUAVAAuAHcARQBCA'
153            - 'TgBFAFQALgB3AEUAQg'
154            - 'OAEUAVAAuAHcARQBCA'
155            - 'TgBlAHQALgBXAEUAQg'
156            - '4AZQB0AC4AVwBFAEIA'
157            - 'OAGUAdAAuAFcARQBCA'
158            - 'bgBFAHQALgBXAEUAQg'
159            - '4ARQB0AC4AVwBFAEIA'
160            - 'uAEUAdAAuAFcARQBCA'
161            - 'TgBFAHQALgBXAEUAQg'
162            - 'OAEUAdAAuAFcARQBCA'
163            - 'bgBlAFQALgBXAEUAQg'
164            - '4AZQBUAC4AVwBFAEIA'
165            - 'uAGUAVAAuAFcARQBCA'
166            - 'TgBlAFQALgBXAEUAQg'
167            - 'OAGUAVAAuAFcARQBCA'
168            - 'bgBFAFQALgBXAEUAQg'
169            - '4ARQBUAC4AVwBFAEIA'
170            - 'uAEUAVAAuAFcARQBCA'
171    condition: all of selection_*
172falsepositives:
173    - Unknown
174level: high

References

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