PowerShell Token Obfuscation (SigmaHQ#3825)

Co-authored-by: Nasreddine Bencherchali <[email protected]>

rules/windows/powershell/powershell_script/posh_ps_token_obfuscation.yml

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+title: Powershell Token Obfuscation - Powershell
+id: f3a98ce4-6164-4dd4-867c-4d83de7eca51
+related:
+    - id: deb9b646-a508-44ee-b7c9-d8965921c6b6
+      type: similar
+status: experimental
+description: Detects TOKEN OBFUSCATION technique from Invoke-Obfuscation
+references:
+    - https://github.com/danielbohannon/Invoke-Obfuscation
+author: frack113
+date: 2022/12/27
+tags:
+    - attack.defense_evasion
+    - attack.t1027.009
+logsource:
+    product: windows
+    category: ps_script
+    definition: Script block logging must be enabled
+detection:
+    selection:
+        # Examples:
+        #   IN`V`o`Ke-eXp`ResSIOn (Ne`W-ob`ject Net.WebClient).DownloadString
+        #   &('In'+'voke-Expressi'+'o'+'n') (.('New-Ob'+'jec'+'t') Net.WebClient).DownloadString
+        #   &("{2}{3}{0}{4}{1}"-f 'e','Expression','I','nvok','-') (&("{0}{1}{2}"-f'N','ew-O','bject') Net.WebClient).DownloadString
+        #   ${e`Nv:pATh}
+        - ScriptBlockText|re: '\w+\`(\w+|-|.)\`[\w+|\s]'
+        #- ScriptBlockText|re: '\((\'(\w|-|\.)+\'\+)+\'(\w|-|\.)+\'\)' TODO: fixme
+        - ScriptBlockText|re: '"({\d})+"\s*-f'
+        - ScriptBlockText|re: '\${((e|n|v)*`(e|n|v)*)+:path}|\${((e|n|v)*`(e|n|v)*)+:((p|a|t|h)*`(p|a|t|h)*)+}|\${env:((p|a|t|h)*`(p|a|t|h)*)+}'
+    condition: selection
+falsepositives:
+    - Unknown
+level: high

rules/windows/process_creation/proc_creation_win_powershell_token_obfuscation.yml

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+title: Powershell Token Obfuscation - Process Creation
+id: deb9b646-a508-44ee-b7c9-d8965921c6b6
+related:
+    - id: f3a98ce4-6164-4dd4-867c-4d83de7eca51
+      type: similar
+status: experimental
+description: Detects TOKEN OBFUSCATION technique from Invoke-Obfuscation
+references:
+    - https://github.com/danielbohannon/Invoke-Obfuscation
+author: frack113
+date: 2022/12/27
+tags:
+    - attack.defense_evasion
+    - attack.t1027.009
+logsource:
+    category: process_creation
+    product: windows
+detection:
+    selection:
+        # Examples:
+        #   IN`V`o`Ke-eXp`ResSIOn (Ne`W-ob`ject Net.WebClient).DownloadString
+        #   &('In'+'voke-Expressi'+'o'+'n') (.('New-Ob'+'jec'+'t') Net.WebClient).DownloadString
+        #   &("{2}{3}{0}{4}{1}"-f 'e','Expression','I','nvok','-') (&("{0}{1}{2}"-f'N','ew-O','bject') Net.WebClient).DownloadString
+        #   ${e`Nv:pATh}
+        - CommandLine|re: '\w+\`(\w+|-|.)\`[\w+|\s]'
+        #- CommandLine|re: '\((\'(\w|-|\.)+\'\+)+\'(\w|-|\.)+\'\)' TODO: fixme
+        - CommandLine|re: '\"({\d})+\"\s*-f'
+        - CommandLine|re: '\${((e|n|v)*`(e|n|v)*)+:path}|\${((e|n|v)*`(e|n|v)*)+:((p|a|t|h)*`(p|a|t|h)*)+}|\${env:((p|a|t|h)*`(p|a|t|h)*)+}'
+    condition: selection
+falsepositives:
+    - Unknown
+level: high