EPWv12

Hunt Hypothesis

This rule targets specific memory patterns associated with the EPWv12 YARA signature, indicating the presence of a known malware variant or exploit kit component within the environment. Proactively hunting for this signature allows the SOC to identify low-severity threats that may be used for initial access or lateral movement before they escalate into more impactful attacks.

YARA Rule

rule EPWv12
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 06 57 1E 56 55 52 51 53 50 2E [4] 8C C0 05 [2] 2E [3] 8E D8 A1 [2] 2E }

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

• Microsoft Defender for Endpoint (MDE) Real-Time Protection Scans: The MDE agent (MsMpEng.exe) frequently performs deep memory scans and file integrity checks on active processes, which can temporarily match generic YARA patterns like EPWv12 if the rule targets common library structures or embedded resources.
  • Filter/Exclusion: Exclude processes where the parent is MsMpEng.exe or SecurityHealthSystray.exe, or filter out events where the Image path contains \Program Files\Windows Defender\.
• Visual Studio Code (VS Code) Extension Host: The extensionHost.exe process loads numerous Node.js modules and native extensions (e.g., Python, C/C++, or ESLint) that may contain compiled binaries or large text buffers matching the byte patterns defined in EPWv12.
  • Filter/Exclusion: Exclude processes where the Image path ends with \Code\ or \VSCode\ and the process name is extensionHost.exe or node.exe spawned by it.
• Adobe Creative Cloud Update Service: The AdobeUpdateService.exe or AdobeGenuineSoftwareIntegrityService.exe processes often download and verify large installer packages or license files in memory, which can trigger YARA rules targeting specific binary headers or version strings.
  • Filter/Exclusion: Exclude processes where the Image path contains \Adobe\ and the process name matches AdobeUpdateService.exe, AdobeGenuineSoftwareIntegrityService.exe, or AdobeIPCBroker.exe.
• IntelliJ IDEA / JetBrains IDEs: Java-based IDEs like IntelliJ IDEA (idea64.exe or javaw.exe) load extensive JAR files and native plugins into memory. If EPWv12 targets common Java class structures or specific plugin signatures, these