Suspicious Execution of Powershell with Base64

 1title: Suspicious Execution of Powershell with Base64
 2id: fb843269-508c-4b76-8b8d-88679db22ce7
 3status: test
 4description: Commandline to launch powershell with a base64 payload
 5references:
 6    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1059.001/T1059.001.md#atomic-test-20---powershell-invoke-known-malicious-cmdlets
 7    - https://unit42.paloaltonetworks.com/unit42-pulling-back-the-curtains-on-encodedcommand-powershell-attacks/
 8    - https://mikefrobbins.com/2017/06/15/simple-obfuscation-with-powershell-using-base64-encoding/
 9author: frack113
10date: 2022/01/02
11modified: 2023/01/05
12tags:
13    - attack.execution
14    - attack.t1059.001
15logsource:
16    category: process_creation
17    product: windows
18detection:
19    selection:
20        Image|endswith:
21            - \powershell.exe
22            - \pwsh.exe
23        CommandLine|contains:
24            - ' -e '
25            - ' -en '
26            - ' -enc '
27            - ' -enco'
28            - ' -ec '
29    filter_encoding:
30        CommandLine|contains: ' -Encoding '
31    filter_azure:
32        ParentImage|contains:
33            - 'C:\Packages\Plugins\Microsoft.GuestConfiguration.ConfigurationforWindows\'
34            - '\gc_worker.exe'
35    condition: selection and not 1 of filter_*
36falsepositives:
37    - Unknown
38level: medium

References

• atomic-red-team/atomics/T1059.001/T1059.001.md at f339e7da7d05f6057fdfcdd3742bfcf365fee2a9 · redcanaryco/atomic-red-team

  

  Small and highly portable detection tests based on MITRE's ATT&CK. - redcanaryco/atomic-red-team

  
  Read More

• Pulling Back the Curtains on EncodedCommand PowerShell Attacks

  

  This post is also available in: 日本語 (Japanese)A note to readers: The code samples included within this blog post may trigger alerts from your security software. Please note that this does not indicate an infection or an attack; rather, it is a notification that the code could be malicious if it were live. PowerShell has...

  
  Read More

• https://mikefrobbins.com/2017/06/15/simple-obfuscation-with-powershell-using-base64-encoding/

  
  Read More

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