RLPackFullEdition117DLLaPLibAp0x

Hunt Hypothesis

This YARA rule targets specific memory patterns associated with the RLPackFullEdition117 DLL, indicating the potential presence of a packed or obfuscated library often used for code injection or persistence. Proactively hunting for this signature allows the SOC team to identify stealthy malware components that may evade standard behavioral detections by masking their true functionality within the process memory.

YARA Rule

rule RLPackFullEdition117DLLaPLibAp0x
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 80 7C 24 08 01 0F 85 [4] 60 E8 00 00 00 00 8B 2C 24 83 C4 04 8D B5 53 03 00 00 8D 9D 02 02 00 00 33 FF E8 [4] EB 0F FF 74 37 04 FF 34 37 FF D3 83 C4 08 83 C7 08 83 3C 37 00 75 }

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 specific false positive scenarios for the YARA rule RLPackFullEdition117DLLaPLibAp0x, which likely targets a specific version of the RLPack (or similar packing library) DLL often found in legacy or third-party applications.

• Legacy Java Application Server Updates (e.g., WebLogic, JBoss)

  • Scenario: During a scheduled patching window, the Java Virtual Machine (JVM) or associated native libraries (such as libjvm.so or specific JNI bridges) may be updated. If the vendor bundles a statically linked or dynamically loaded library that shares the same internal structure or signature as the targeted RLPack DLL, the file on disk may match the YARA rule before being loaded into memory.
  • Filter/Exclusion: Exclude files located in standard Java installation directories (e.g., C:\Program Files\Java\, C:\Program Files (x86)\Java\) or specific WebLogic/JBoss installation paths (C:\WebLogic\, C:\JBoss\) if the hash of the file matches a known good baseline for that vendor version.

• Third-Party Antivirus/EDR Driver Updates

  • Scenario: Major security vendors (e.g., CrowdStrike, SentinelOne, Carbon Black) frequently update their kernel-mode drivers or user-mode agents. Some of these agents use custom packing or obfuscation techniques for their core DLLs to protect against tampering. If the update process writes a new version of a core DLL that coincidentally matches the byte pattern of RLPackFullEdition117, it will trigger the rule.
  • Filter/Exclusion: Exclude files owned by known security vendor processes (e.g., FalconSensor.exe, SentinelOne.exe, CarbonBlack.exe) or located in their specific installation directories (e.g., `