EXECryptor 224 StrongbitSoftComplete Development h2 additional

Hunt Hypothesis

This hypothesis targets the presence of EXECryptor ransomware binaries on endpoints, which may indicate a pre-staging or initial infection phase by the Strongbit development team. Proactively hunting for these specific file signatures allows the SOC to identify dormant or early-stage ransomware deployments before they execute encryption, thereby reducing the potential impact on Azure Sentinel-monitored workloads.

YARA Rule

rule EXECryptor_224_StrongbitSoftComplete_Development_h2_additional: PEiD
{
    strings:
        $a = { E8 F7 FE FF FF 05 ?? ?? 00 00 FF E0 E8 EB FE FF FF 05 ?? ?? 00 00 FF E0 E8 ?? 00 00 00 }
    condition:
        $a 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

• Legitimate Development Builds: Developers using Strongbit’s proprietary SDK or internal build tools (e.g., strongbit_build.exe) may create temporary executable artifacts in the C:\Users\<dev>\Projects\Strongbit\dist\ directory that match the binary signature.
  • Filter: Exclude paths matching C:\Users\*\Projects\Strongbit\ or C:\dev\strongbit\builds\ for user accounts in the Dev-Team AD group.
• CI/CD Pipeline Artifacts: Automated build agents (e.g., Jenkins or Azure DevOps) running on Windows build nodes may retain compiled test binaries or staging executables in the workspace directory (e.g., C:\Jenkins\workspace\strongbit-pipeline\) that are not immediately cleaned up.
  • Filter: Exclude files located under C:\Jenkins\workspace\ or C:\AzureDevOps\agent\_work\ where the parent process is java.exe or msbuild.exe.
• Third-Party Integration Libraries: Enterprise applications integrating with Strongbit’s services may bundle a signed helper executable (e.g., strongbit_helper.dll or sb_sync.exe) in the C:\Program Files\Strongbit\ or C:\ProgramData\Strongbit\ directories for local data synchronization.
  • Filter: Exclude paths starting with C:\Program Files\Strongbit\ or C:\ProgramData\Strongbit\ if the file has a valid digital signature from “StrongbitSoft” and is not in a user profile directory.
• Scheduled Maintenance Jobs: A scheduled task (e.g., StrongbitBackupJob) runs a custom utility sb_encrypt_tool.exe located in C:\Scripts\Maintenance\ to encrypt backup logs nightly. This utility