Splasherv10v30

Hunt Hypothesis

This rule targets the presence of the Splasherv10v30 malware variant, which is often used for initial access or persistence through memory injection and process hollowing techniques. Proactively hunting for this signature allows the SOC team to identify compromised hosts early in the kill chain, enabling rapid containment before the adversary establishes lateral movement or exfiltrates data within the Azure environment.

YARA Rule

rule Splasherv10v30
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 9C 60 8B 44 24 24 E8 [4] 5D 81 ED [4] 50 E8 ED 02 [2] 8C C0 0F 84 }

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 runs a local build script that invokes splashserv.exe (or a similarly named helper binary) to generate UI assets or initialize a service wrapper during a CI/CD pipeline execution on a build agent.
  • Filter/Exclusion: Exclude processes where the parent process is a known build tool (e.g., msbuild.exe, dotnet.exe, npm.exe, or python.exe) and the working directory is within a standard source code repository path (e.g., C:\src\, D:\builds\).
• Scenario: An IT administrator manually executes splashserv10v30.exe from a network share or USB drive to troubleshoot a stuck service or apply a hotfix to a specific application server, bypassing the standard software inventory.
  • Filter/Exclusion: Allow execution if the process image path contains \\ (indicating a network share) or if the user account belongs to a specific privileged group (e.g., Domain Admins, Service Desk) and the process is initiated from an interactive session (Logon Type 2 or 10).
• Scenario: A scheduled task defined by a third-party vendor (e.g., a monitoring agent or backup software) launches splashserv10v30.exe as a child process to update its configuration or restart a dependent component at 02:00 AM.
  • Filter/Exclusion: Exclude if the parent process is svchost.exe (specifically the Schedule service) or taskschd.exe, and the command line arguments contain typical maintenance flags (e.g., /update, /config, /restart).
• Scenario: A legacy application installer or updater uses splashserv10v30.exe as a temporary splash screen generator during a silent