MZ0oPE106bTaskFall

Hunt Hypothesis

This detection identifies potential adversary activity involving the execution of suspicious processes matching the “MZ0oPE106bTaskFall” signature, which may indicate early-stage reconnaissance or lateral movement attempts within the environment. A proactive hunt is essential in Azure Sentinel to validate these low-severity alerts against known benign baselines and uncover stealthy threats that might otherwise remain undetected by standard automated responses.

YARA Rule

rule MZ0oPE106bTaskFall
{
      meta:
		author="malware-lu"
strings:
		$a0 = { EB CA 89 03 83 C3 04 87 FE 32 C0 AE 75 FD 87 FE 80 3E FF 75 E2 46 5B 83 C3 04 53 8B 1B 80 3F FF 75 C9 8B E5 61 68 [4] C3 }
	$a1 = { EB CA 89 03 83 C3 04 87 FE 32 C0 AE 75 FD 87 FE 80 3E FF 75 E2 46 5B 83 C3 04 53 8B 1B 80 3F FF 75 C9 8B E5 61 68 [4] C3 FC B2 80 33 DB A4 B3 02 E8 6D 00 00 00 73 F6 33 C9 E8 64 00 00 00 73 1C 33 C0 E8 5B 00 00 00 73 23 B3 02 41 B0 10 E8 4F 00 00 00 12 C0 73 F7 75 3F AA EB D4 E8 4D 00 00 00 2B CB 75 10 E8 42 00 00 00 EB 28 AC D1 E8 74 4C 13 C9 EB 1C 91 48 C1 E0 08 AC E8 2C 00 00 00 3D 00 7D 00 00 73 0A 80 FC 05 73 06 83 F8 7F 77 02 41 41 95 8B C5 B3 01 56 8B F7 2B F0 F3 A4 5E EB 8E 02 D2 75 05 8A 16 46 12 D2 C3 33 C9 41 E8 EE FF FF FF 13 C9 E8 E7 FF FF FF 72 F2 C3 }

condition:
		$a0 at pe.entry_point or $a1 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 2 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the MZ0oPE106bTaskFall detection rule, including suggested filters and exclusions:

• Scenario: Scheduled Antivirus Full Scan Execution

  • Context: Enterprise endpoint protection suites (e.g., Microsoft Defender, CrowdStrike Falcon) often run scheduled full scans during off-hours. These scans frequently spawn new tasks or modify existing task configurations to manage resource usage, which can trigger the “TaskFall” logic if the rule monitors for unexpected task creation or modification by security tools.
  • Suggested Filter/Exclusion: Create an exclusion based on the parent process name and file path.
    • Filter: Exclude if Parent_Process_Name IN ('MsMpEng.exe', 'FalconSensorService.exe') AND File_Path contains '\Program Files\Microsoft Defender\' OR '\CrowdStrike\Falcon\'.

• Scenario: Automated Patch Management Deployment

  • Context: Systems management tools like Microsoft Endpoint Configuration Manager (SCCM) or Ivanti Control often deploy updates via scheduled tasks. When a patch is pushed, the tool creates a temporary task to execute the installer (msiexec.exe), which may match the signature of a suspicious task creation event defined in the YARA rule.
  • Suggested Filter/Exclusion: Exclude events where the command line contains specific patch management keywords or originates from known management servers.
    • Filter: Exclude if Command_Line contains '/quiet' AND Parent_Process_Name IN ('ccmexec.exe', 'IvantiControlAgent.exe').

• Scenario: Backup Agent Job Initialization

  • Context: Enterprise backup solutions such as Veeam or Rubrik run scheduled jobs that spawn new tasks to initiate data transfer. These agents often register new Windows Scheduled Tasks dynamically to handle incremental backups, which can be flagged as a potential “TaskFall