Yoda Crypter 1.2

Hunt Hypothesis

This rule detects the execution of the Yoda Crypter 1.2, a known malware variant that adversaries deploy to encrypt files and establish persistence on compromised hosts. Proactively hunting for this specific crypter in Azure Sentinel allows the SOC team to identify early-stage ransomware activity or cryptominer deployments before they propagate across the environment.

YARA Rule

rule yoda_crypter_1_2 : Crypter
{
	meta:
		author="Kevin Falcoz"
		date_create="15/04/2013"
		description="Yoda Crypter 1.2"

	strings:
		$signature1={60 E8 00 00 00 00 5D 81 ED F3 1D 40 00 B9 7B 09 00 00 8D BD 3B 1E 40 00 8B F7 AC [19] EB 01 [27] AA E2 CC}

	condition:
		$signature1 at pe.entry_point
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: A DevOps engineer uses Yoda Crypter 1.2 to obfuscate a PowerShell script or C# binary before deploying it as a scheduled task on a build server to protect source code from casual inspection.
  • Filter/Exclusion: Exclude processes where the parent process is a known build tool (e.g., msbuild.exe, dotnet.exe, npm.exe) or where the command line contains specific build-related flags (e.g., /obfuscate, --crypt).
• Scenario: A security team member runs Yoda Crypter 1.2 in a sandboxed test environment or isolated VM to validate detection coverage for new malware samples.
  • Filter/Exclusion: Exclude events originating from hosts tagged with Environment=Lab or Role=Sandbox in your asset inventory, or exclude if the user account belongs to the SecurityOps or RedTeam AD group.
• Scenario: An application developer uses Yoda Crypter 1.2 during local development to test how their custom encryption wrapper interacts with the OS, specifically on a developer workstation that is not part of the production fleet.
  • Filter/Exclusion: Exclude events where the source host is categorized as Workstation-Dev or if the executing user is a member of the Developers group and the process is launched from a standard IDE directory (e.g., C:\Users\<User>\source\repos\).
• Scenario: A legacy application installer uses Yoda Crypter 1.2 as a helper tool to encrypt configuration files or small utility binaries during the initial setup phase on a new server.
  • Filter/Exclusion: Correlate with recent installation activity by excluding if the parent process is msiexec.exe or setup.exe, or if