is hex mid mandibule32

Hunt Hypothesis

This detection targets adversaries executing custom or obfuscated payloads identified by the is__hex_mid_mandibule32 signature, which may indicate early-stage reconnaissance or lateral movement activities within the environment. Proactively hunting for this low-severity indicator in Azure Sentinel is critical to uncover stealthy threats that might bypass standard high-fidelity alerts and establish a baseline for future anomaly detection.

YARA Rule

rule is__hex_mid_mandibule32 {
	meta:
		author = "unixfreaxjp"
		date = "2018-06-01"
	strings:
		$hex05 = { E8 09 07 00 00 81 C1 FC 1F 00 00 8D 81 26 E1 FF FF } // st
		$hex06 = { 56 53 83 EC 24 E8 E1 05 00 00 81 C3 D0 1E 00 00 8B 44 24 30} // mn
		$hex07 = { 81 C3 E8 29 00 00 C7 44 24 0C } // pt
		$hex08 = { E8 C6 D5 FF FF 83 C4 0C 68 00 01 00 00 } // ld
	condition:
                3 of them 
}

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 4 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Based on the detection rule is__hex_mid_mandibule32 (which appears to be a YARA signature targeting specific hex patterns often associated with Windows system binaries or mid-tier management agents), here are 4 specific false positive scenarios in an enterprise environment, along with recommended filters:

• Scenario: Scheduled Antivirus Definition Updates

  • Context: Enterprise Endpoint Protection suites (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint) frequently download and stage new definition packages. These processes often spawn temporary workers that match the hex signature of legitimate system management binaries during the update cycle.
  • Filter/Exclusion: Exclude the specific process image paths associated with the AV vendor’s update service (e.g., C:\Program Files\CrowdStrike\fsagent.exe or C:\Windows\System32\MpCmdRun.exe) and restrict the rule to only trigger if the parent process is not a known system scheduler.

• Scenario: Group Policy Object (GPO) Deployment Tasks

  • Context: During business hours, IT administrators push configuration changes via Microsoft System Center Configuration Manager (SCCM) or native Group Policy. The gpupdate.exe and associated background workers often execute scripts that instantiate the specific hex pattern identified by this rule to apply registry keys or software patches.
  • Filter/Exclusion: Create an exclusion for processes launched directly by svchost.exe with the service name gpsvc (Group Policy Client) or ccmexec.exe, limiting alerts to non-standard execution paths outside of %SystemRoot%.

• Scenario: Automated Software Patching Cycles

  • Context: Third-party patch management tools like Ivanti Endpoint Manager or Jamf Pro (for hybrid environments) run nightly jobs to install critical updates. These agents utilize a specific binary structure that