wce

Hunt Hypothesis

This detection identifies Windows Component Extension (WCE) activities that may indicate an adversary establishing persistence or executing custom logic within the Windows environment. Proactively hunting for these signals in Azure Sentinel allows the SOC team to uncover subtle, low-severity anomalies that could represent early-stage lateral movement or stealthy command execution before they escalate into critical incidents.

YARA Rule

rule wce
{
	meta:
		description		= "wce"
		author			= "Benjamin DELPY (gentilkiwi)"
		tool_author		= "Hernan Ochoa (hernano)"

	strings:
		$hex_legacy		= { 8b ff 55 8b ec 6a 00 ff 75 0c ff 75 08 e8 [0-3] 5d c2 08 00 }
		$hex_x86		= { 8d 45 f0 50 8d 45 f8 50 8d 45 e8 50 6a 00 8d 45 fc 50 [0-8] 50 72 69 6d 61 72 79 00 }
		$hex_x64		= { ff f3 48 83 ec 30 48 8b d9 48 8d 15 [0-16] 50 72 69 6d 61 72 79 00 }

	condition:
		any 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 3 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the wce detection rule in an enterprise environment, including suggested filters and exclusions:

• Scenario: Scheduled Backup Jobs via Windows Server Backup or Veeam

  • Context: Automated backup agents (e.g., Veeam Agent, Microsoft System Center Data Protection Manager) frequently trigger the wce event when they perform integrity checks or initiate block-level backups on critical volumes. These jobs often run during off-hours and generate high-volume logs that mimic suspicious activity.
  • Filter/Exclusion: Exclude events where the Source matches known backup service accounts (e.g., VeeamBackupService, SystemCenterDPMSvc) or filter by EventID associated with scheduled task triggers (e.g., TaskName contains “Backup” or “IntegrityCheck”).

• Scenario: Group Policy Updates and Configuration Management

  • Context: During business hours, the enterprise uses tools like Microsoft Endpoint Manager (Intune) or SCCM to push configuration changes. When these agents apply new policies or update registry keys on endpoints, they generate wce events that can be misinterpreted as unauthorized configuration changes by a user.
  • Filter/Exclusion: Create an exclusion rule for events where the ProcessName is ccmexec.exe (SCCM) or IntuneManagementExtension.exe, and the UserAccount is the local system account (NT AUTHORITY\SYSTEM) rather than an interactive user.

• Scenario: Antivirus Real-Time Scanning and Quarantine Operations

  • Context: Endpoint Detection and Response (EDR) solutions such as CrowdStrike Falcon or Microsoft Defender for Endpoint often trigger wce events when they scan large files, update virus definitions, or move suspicious files to quarantine. This is particularly common during the morning startup window when