SmartEMicrosoft

Hunt Hypothesis

This detection identifies potential Microsoft-related threats by leveraging a specialized YARA signature to pinpoint specific file artifacts associated with the “SmartEMicrosoft” pattern within the Azure Sentinel environment. A proactive hunt for this behavior is essential to uncover early-stage indicators of compromise that may evade standard alerting, allowing the SOC team to validate and respond to nuanced Microsoft ecosystem risks before they escalate.

YARA Rule

rule SmartEMicrosoft
{
      meta:
		author="malware-lu"
strings:
		$a0 = { EB 15 03 00 00 00 ?? 00 00 00 00 00 00 00 00 00 00 00 68 00 00 00 00 55 E8 00 00 00 00 5D 81 ED 1D 00 00 00 8B C5 55 60 9C 2B 85 8F 07 00 00 89 85 83 07 00 00 FF 74 24 2C E8 BB 01 00 00 0F 82 2F 06 00 00 E8 8E 04 00 00 49 0F 88 23 06 }

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

False Positive Scenarios for “SmartEMicrosoft” Rule

• Scenario: Microsoft Office 365 ProPlus Background Updates

  • Context: The OfficeClickToRun.exe process frequently launches child processes to download and install cumulative updates, which often mimic the behavior of smart management agents by spawning temporary scripts or modifying registry keys.
  • Filter/Exclusion: Exclude file paths containing C:\Program Files\Microsoft Office Root\Office16\ and process names matching *ClickToRun.exe. Additionally, filter out events where the parent process is msiexec.exe with a command line argument containing /quiet.

• Scenario: Scheduled Antivirus Definition Updates (Windows Defender)

  • Context: The Windows Security service (SenseService) runs scheduled jobs every morning to fetch definition updates from Microsoft Update servers. This activity involves network I/O and temporary file creation that can trigger the YARA rule’s heuristic for “smart” management traffic.
  • Filter/Exclusion: Create an exclusion based on the process name MsMpEng.exe running under the SYSTEM account. Filter out events occurring between 02:00 and 04:00 UTC where the destination port is 443 and the source IP belongs to the Microsoft CDN range (e.g., 13.107.x.x).

• Scenario: Enterprise Configuration Management via SCCM/MECM

  • Context: System Center Configuration Manager (SCCM) agents (ccmexec.exe) push configuration policies and software deployment packages during maintenance windows, often executing PowerShell scripts that resemble the “SmartEMicrosoft” detection signature.
  • Filter/Exclusion: Exclude processes where the parent is ccmexec.exe and the working directory starts with C:\Windows\CCM. Add a rule to ignore events tagged with the