VxEddie2100

Hunt Hypothesis

This detection identifies potential file-based threats matching the specific signature of the VxEddie2100 malware variant through YARA analysis within Azure Sentinel logs. Proactive hunting for this indicator is essential to uncover early-stage infections that may evade standard heuristic controls, allowing the SOC team to isolate affected endpoints before lateral movement occurs.

YARA Rule

rule VxEddie2100
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E8 [2] 4F 4F 0E E8 [2] 47 47 1E FF [2] CB E8 [2] 84 C0 [2] 50 53 56 57 1E 06 B4 51 CD 21 8E C3 [7] 8B F2 B4 2F CD 21 AC }

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 VxEddie2100 detection rule, including suggested filters and exclusions:

• Scenario: Automated Patch Deployment via Microsoft Endpoint Configuration Manager (SCCM)

  • Context: During nightly maintenance windows, SCCM pushes security updates to endpoints. The deployment agent (ccmsetup.exe or WUAUCLT.exe) often executes scripts that match the VxEddie2100 signature due to similar code patterns in update verification modules.
  • Suggested Filter/Exclusion: Create a process exclusion for C:\Windows\CCM\Setup\ccmsetup.exe and C:\Windows\System32\WUAUCLT.exe. Additionally, add a time-based filter to suppress alerts from these processes between 01:00 and 05:00 local time on weekdays.

• Scenario: Scheduled Antivirus Definition Updates by CrowdStrike Falcon

  • Context: The CrowdStrike sensor (csfalcon.exe) periodically downloads and installs new definition packs. This activity triggers the YARA rule because the update installer mimics the behavior of the targeted threat, specifically regarding file hashing and registry key modifications in HKLM\SOFTWARE\CrowdStrike.
  • Suggested Filter/Exclusion: Exclude the process path C:\Program Files\CrowdStrike\FalconSensor\csfalcon.exe from the rule. Alternatively, implement a hash-based exclusion for the known good SHA-256 hashes of the latest Falcon update installer binaries.

• Scenario: Enterprise Backup Job Execution via Veeam Backup & Replication

  • Context: The Veeam service (Veeam.Backup.Service.exe) initiates backup jobs that involve scanning and compressing large datasets. The compression engine utilizes a library that shares structural similarities with the detection logic of VxE