Packmanv0001

Hunt Hypothesis

This hypothesis detects the execution of a specific malicious payload identified by the Packmanv0001 YARA signature within Azure Sentinel’s file integrity monitoring data. Proactive hunting for this indicator is essential to uncover early-stage adversary activity that may be missed by standard alerting, allowing the SOC team to investigate potential low-severity threats before they escalate into significant incidents.

YARA Rule

rule Packmanv0001
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 E8 00 00 00 00 58 8D A8 [2] FF FF 8D 98 [3] FF 8D [2] 01 00 00 [28] 00 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 Packmanv0001 detection rule in an enterprise environment, along with suggested filters and exclusions:

• Scenario: Automated Software Deployment via SCCM/Intune

  • Context: The System Center Configuration Manager (SCCM) or Microsoft Intune agent executes a scheduled deployment task that unpacks application installers (e.g., .msi or .cab files) in the C:\Windows\CCMCache directory. This extraction process often triggers the YARA rule due to the presence of compressed archives and temporary unpacking scripts.
  • Suggested Filter/Exclusion: Add a path-based exclusion for the deployment cache directories: C:\Windows\CCMCache\* and C:\ProgramData\Microsoft\IntuneManagementExtension\Logs. Additionally, exclude processes running under the ccmexec.exe or Microsoft.IntuneManagementEngine.Service service accounts.

• Scenario: Antivirus Real-Time Scanning of Archive Files

  • Context: Enterprise Endpoint Protection (e.g., CrowdStrike Falcon or Microsoft Defender for Endpoint) performs real-time scanning on large zip archives downloaded by users to the C:\Users\<User>\Downloads folder. The YARA rule may flag the internal structure of these compressed files as a potential “packer” signature when the AV engine extracts them in memory before writing to disk.
  • Suggested Filter/Exclusion: Configure an exclusion for the process MsMpEng.exe (Defender) or FalconSensorService.exe (CrowdStrike) specifically when accessing files within the Downloads directory. You can also add a file extension filter to ignore .zip, .7z, and .tar.gz files if they are not being executed immediately upon extraction.

• **Scenario: Scheduled Backup Job Utilizing Veeam