TPACKv05cm2

Hunt Hypothesis

This detection identifies potential file-based threats by matching artifacts against the specific YARA signature defined in TPACKv05cm2, which may indicate known malware or suspicious application behavior within the environment. Proactively hunting for this signal allows the SOC team to validate low-severity alerts that could represent early-stage compromises or benign false positives, ensuring comprehensive coverage of file integrity and reducing the risk of undetected lateral movement in Azure Sentinel.

YARA Rule

rule TPACKv05cm2
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 68 [2] FD 60 BE [2] BF [2] B9 [2] F3 A4 8B F7 BF [2] FC 46 E9 CE FD }

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 TPACKv05cm2 detection rule, including suggested filters and exclusions tailored for a legitimate enterprise environment:

• Scenario: Scheduled Antivirus Definition Updates

  • Context: The YARA rule flags the mpcmd.exe process (Microsoft Defender) or avpcc.exe (Kaspersky) when it spawns child processes to download and install new virus definition packages during off-hours. These updates often involve unpacking compressed archives that mimic the signature of a malicious tool package.
  • Suggested Filter/Exclusion: Create an exclusion rule based on the parent process name (mpcmd.exe or avpcc.exe) and restrict the match to specific file paths, such as C:\ProgramData\Microsoft\Windows Defender\ or C:\Program Files\Kaspersky Lab\. Additionally, limit the alert trigger to business hours (e.g., 09:00–17:00) if updates are configured for off-hours.

• Scenario: Admin Deployment via SCCM/Intune

  • Context: System administrators use Microsoft Endpoint Configuration Manager (SCCM) or Intune to push software packages (e.g., Office 365 updates, Adobe Creative Cloud) to endpoints. The deployment agent (ccmexec.exe) extracts the installation package in a temporary directory, triggering the TPACKv05cm2 signature due to the presence of embedded installer scripts and compressed binaries.
  • Suggested Filter/Exclusion: Exclude processes where the parent is ccmexec.exe or msiexec.exe. Implement a path-based exclusion for known deployment directories like C:\Windows\CCM\Cache\ or C:\ProgramData\Microsoft\Intune Management Extension\.

• Scenario: Automated Backup and Archiving Jobs