Create proc_creation_win_powershell_aes_decrypt.yml

emmenhtal/proc_creation_win_powershell_aes_decrypt.yml

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+title: Potential AES-encrypted PowerShell patterns in CommandLine
+id: 47be590d-4a9e-4ab1-b9f6-a332709c2100
+status: stable
+description: |
+    Detects suspicious execution of Powershell commands related to AES Encryption.
+    This could be an indicator of use of Powershell to decrypt additionnal payload as observed during Emmenhtal infection.
+references: https://www.orangecyberdefense.com/global/blog/cert-news/emmenhtal-a-little-known-loader-distributing-commodity-infostealers-worldwide
+author: Orange Cyberdefense - Florian SIMONET
+date: 2024/08/09
+tags:
+    - attack.execution
+    - attack.defense_evasion
+    - attack.t1059.001
+    - attack.t1140
+    - tlp.white
+logsource:
+    product: windows
+    category: process_creation
+detection:
+    selection_img:
+        Image|endswith:
+            - '\powershell.exe'
+            - '\pwsh.exe'
+        OriginalFileName:
+            - 'PowerShell.EXE'
+            - 'pwsh.dll'
+    selection_cmdline:
+        CommandLine|contains|all:
+            - 'System.Security.Cryptography.Aes'
+            - 'CreateDecryptor'
+    condition: all of selection_*
+falsepositives:
+    - Unknown
+level: medium