PowerShell Script with Encryption/Decryption Capabilities

Identifies the use of Cmdlets and methods related to encryption/decryption of files in PowerShell scripts, which malware and offensive security tools can abuse to encrypt data or decrypt payloads to bypass security solutions.

Rule type: query

Rule indices:

winlogbeat-*
logs-windows.*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References: None

Tags:

Elastic
Host
Windows
Threat Detection
Defense Evasion
PowerShell

Version: 1

Rule authors:

Elastic

Rule license: Elastic License v2

Rule query

edit

event.category:process and
  powershell.file.script_block_text : (
    (
      "Cryptography.AESManaged" or
      "Cryptography.RijndaelManaged" or
      "Cryptography.SHA1Managed" or
      "Cryptography.SHA256Managed" or
      "Cryptography.SHA384Managed" or
      "Cryptography.SHA512Managed" or
      "Cryptography.SymmetricAlgorithm" or
      "PasswordDeriveBytes" or
      "Rfc2898DeriveBytes"
    ) and
    (
      CipherMode and PaddingMode
    ) and
    (
      ".CreateEncryptor" or
      ".CreateDecryptor"
    )
  ) and not user.id : "S-1-5-18"

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Deobfuscate/Decode Files or Information
- ID: T1140
- Reference URL: https://attack.mitre.org/techniques/T1140/
Technique:
- Name: Obfuscated Files or Information
- ID: T1027
- Reference URL: https://attack.mitre.org/techniques/T1027/

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