RLPackV10betaap0x

Hunt Hypothesis

This detection identifies the presence of a specific packed executable signature (RLPackV10betaap0x) that may indicate an adversary utilizing obfuscation techniques to conceal malicious payloads within legitimate applications. Proactively hunting for this pattern in Azure Sentinel allows the SOC team to uncover stealthy threats that might evade standard signature-based defenses by analyzing file attributes and process behaviors associated with this packing mechanism.

YARA Rule

rule RLPackV10betaap0x
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 E8 00 00 00 00 8D 64 24 04 8B 6C 24 FC 8D B5 4C 02 00 00 8D 9D 13 01 00 00 33 FF EB 0F FF 74 37 04 FF 34 37 FF D3 83 C4 08 83 C7 08 83 3C 37 00 75 EB }

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 RLPackV10betaap0x detection rule, along with targeted filtering strategies:

• Scenario: Scheduled Antivirus Definition Updates via Microsoft Defender

  • Context: The daily automated update job for Microsoft Defender for Endpoint (or similar AV like CrowdStrike) often downloads and unpacks definition packages that match the RLPackV10betaap0x signature structure. These updates are typically triggered by the Windows Task Scheduler or the service itself during off-hours.
  • Filter/Exclusion: Exclude processes where the executable path matches C:\Program Files\Microsoft Defender\MpCmdRun.exe or C:\ProgramData\Microsoft\Windows Defender\Platform\<version>\mpclient.dll, specifically when triggered by the “Windows Defender Update” scheduled task ({...}).

• Scenario: Deployment of Internal Patching Packages via SCCM/Intune

  • Context: System Center Configuration Manager (SCCM) or Microsoft Intune frequently deploys application patches that utilize a proprietary packing format similar to the rule’s logic. When an agent on a workstation receives and extracts these payloads during business hours, it triggers the YARA match.
  • Filter/Exclusion: Create a filter to ignore alerts where the parent process is ccmexec.exe (SCCM) or Microsoft.IntuneManagementExtension.exe, and the file extension of the quarantined artifact is .msi or .cab.

• Scenario: Backup Agent Data Compression Jobs

  • Context: Enterprise backup solutions like Veeam Backup & Replication or Commvault often run compression agents that package data into archives. The internal logic of these agents uses a binary structure identical to the RLPackV10betaap0x signature when creating temporary staging files before final upload.
  • **Filter/