Defense Evasion (TA0005)(external, opens in a new tab or window)
text code block:event.category:process and host.os.type:windows 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" and not ( file.name : "Bootstrap.Octopus.FunctionAppenderContext.ps1" and powershell.file.script_block_text : ("function Decrypt-Variables" or "github.com/OctopusDeploy") )
Install detection rules in Elastic Security
Detect PowerShell Script with Encryption/Decryption Capabilities in the Elastic Security detection engine by installing this rule into your Elastic Stack.
To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(external, opens in a new tab or window).