SplashBitmapv100BoBBobsoft

Hunt Hypothesis

This detection targets potential malicious activity associated with the SplashBitmapv100BoBBobsoft signature, which may indicate the presence of specific software components or obfuscated payloads within the environment. Proactively hunting for this indicator in Azure Sentinel allows the SOC team to identify early-stage anomalies and validate whether these artifacts represent legitimate business applications or emerging threats requiring further investigation.

YARA Rule

rule SplashBitmapv100BoBBobsoft
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E8 00 00 00 00 60 8B 6C 24 20 55 81 ED [4] 8D BD [4] 8D 8D [4] 29 F9 31 C0 FC F3 AA 8B 04 24 48 66 25 00 F0 66 81 38 4D 5A 75 F4 8B 48 3C 81 3C 01 50 45 00 00 75 E8 89 85 [4] 8D BD [4] 6A 00 }

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

Here are 4 specific false positive scenarios for the SplashBitmapv100BoBBobsoft detection rule, including suggested filters and exclusions:

• Scenario: Legitimate deployment of BobSoft’s “BobSoft Splash Bitmap” component via Microsoft System Center Configuration Manager (SCCM) or Intune.

  • Context: During scheduled maintenance windows, the endpoint management tool pushes updates to the SplashBitmapv100 module across the enterprise fleet. The YARA rule triggers because the executable matches the BobSoft signature during installation or patching.
  • Suggested Filter/Exclusion: Create a whitelist exclusion based on the specific file path and publisher. Exclude files located in C:\Program Files\BobSoft\SplashBitmapv100\ that have a valid digital signature from “BobSoft GmbH” (or relevant certificate authority).

• Scenario: Execution of a scheduled PowerShell job for UI rendering optimization in the HR or CRM department.

  • Context: A nightly scheduled task (Task Scheduler) runs a custom script to generate splash screens for internal dashboards, invoking the SplashBitmapv100BoBBobsoft.dll or executable as part of the workflow. This is common in environments using BobSoft’s integration layer.
  • Suggested Filter/Exclusion: Add an exclusion based on the parent process name and command line arguments. Exclude detections where the parent process is powershell.exe or svchost.exe running under a specific service account (e.g., DOMAIN\HR-Service-Account) with the command line containing “BobSoft”.

• Scenario: End-user interaction with BobSoft’s Document Management System (DMS) during high-volume printing.

  • Context: Users in the Finance department frequently print large reports through the BobSoft DMS client. The client utilizes the `SplashBitmapv1