SDProtectorV11xRandyLi

Hunt Hypothesis

This hypothesis targets the presence of the SDProtector V11x ransomware variant, specifically associated with the actor RandyLi, which is known for encrypting files and deploying a custom recovery mechanism. Proactively hunting for this signature in Azure Sentinel allows the SOC to identify early-stage infections or dormant payloads before the encryption process begins, minimizing potential data loss and operational disruption.

YARA Rule

rule SDProtectorV11xRandyLi
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 6A FF 68 [4] 68 88 88 88 08 64 A1 }

condition:
		$a0 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 developer or DevOps engineer uses SDProtector to obfuscate a proprietary .NET application or C# library before deploying it to a staging environment or packaging it for a client. The YARA rule matches the specific header or string patterns of the SDProtector v11.x container, flagging the executable or DLL as malicious.

  • Filter/Exclusion: Exclude files located in specific development directories (e.g., C:\Projects\, C:\Builds\, or C:\Artifacts\) and exclude processes spawned by build tools like MSBuild.exe, dotnet.exe, or NuGet.exe that are writing these files to disk.

• Scenario: An IT administrator runs a scheduled PowerShell script or a Task Scheduler job to apply a custom patch or update to a legacy internal tool that was compiled using SDProtector. The rule triggers on the execution of the patched binary or the temporary extraction of the protected payload during the update process.

  • Filter/Exclusion: Exclude executions where the parent process is svchost.exe (specifically the Task Scheduler service) or powershell.exe running from a trusted admin path (e.g., C:\Admin\Scripts\), and exclude files with a .tmp extension in the %TEMP% directory that are created and deleted within a short time window (< 30 seconds).

• Scenario: A security team or QA engineer uses SDProtector to create a test binary for verifying endpoint detection coverage or to simulate a specific threat scenario in a sandboxed environment. The rule fires on the test executable running in a designated test VM or container.

  • Filter/Exclusion: Exclude hosts with a specific tag (e.g., env=staging, env=sandbox, or role=qa) in the asset inventory,