Invocation Of Crypto-Classes From The "Cryptography" PowerShell Namespace

A Sigma rule for process creation on Windows, from SigmaHQ’s threat hunting rules, by Andreas Braathen (mnemonic.io).

medium 2 ATT&CK techniques 2 programs it names

What it looks for

its detection, as SigmaHQ writes it

detection:
  selection_cmdlet_classes:
    CommandLine|contains:
      - '.AesCryptoServiceProvider'
      - '.DESCryptoServiceProvider'
      - '.DSACryptoServiceProvider'
      - '.RC2CryptoServiceProvider'
      - '.Rijndael'
      - '.RSACryptoServiceProvider'
      - '.TripleDESCryptoServiceProvider'
  selection_cmdlet_namespace:
    CommandLine|contains: 'System.Security.Cryptography.'
  selection_img:
    - Image|endswith:
        - '\powershell.exe'
        - '\pwsh.exe'
    - OriginalFileName:
        - 'PowerShell.EXE'
        - 'pwsh.dll'
  condition: all of selection_*

The rule’s detection, its selections and fields in order of name. The whole rule, with its references and false positives, is on SigmaHQ, by Andreas Braathen (mnemonic.io), under the Detection Rule License 1.1. CmdID evaluates it on a command line alone: a test on what a command line cannot show, such as the parent process or the user, is not met.

None of the everyday examples and documented commands on CmdID’s program pages trips it. To see whether a command line does, paste it into CmdID.

Programs and files it names

their pages here

powershellpowershell.exe

ATT&CK

the techniques it is tagged with

T1027.010Obfuscated Files or Information: Command Obfuscation

T1059.001Command and Scripting Interpreter: PowerShell

Invocation Of Crypto-Classes From The "Cryptography" PowerShell Namespace

What it looks for

Programs and files it names

ATT&CK

Other rules for T1027.010 Obfuscated Files or Information: Command Obfuscation