eXPressorv1451CGSoftLabs

Hunt Hypothesis

This detection identifies potential execution of malicious or suspicious binaries matching the CG Soft Labs signature pattern within the Azure Sentinel environment. Proactively hunting for this behavior allows the SOC team to validate legitimate software usage and uncover early-stage threats that may evade standard high-severity alerts due to their low initial severity classification.

YARA Rule

rule eXPressorv1451CGSoftLabs
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 83 EC 58 53 56 57 83 65 DC 00 F3 EB 0C 65 58 50 72 2D 76 2E 31 2E 34 2E 00 A1 00 [3] 05 00 [3] A3 08 [3] A1 08 [3] B9 81 [3] 2B 48 18 89 0D 0C [3] 83 3D 10 [3] 00 74 16 A1 08 [3] 8B 0D 0C [3] 03 48 14 }
	$a1 = { 55 8B EC 83 EC 58 53 56 57 83 65 DC 00 F3 EB 0C 65 58 50 72 2D 76 2E 31 2E 34 2E 00 A1 00 [3] 05 00 [3] A3 08 [3] A1 08 [3] B9 81 [3] 2B 48 18 89 0D 0C [3] 83 3D 10 [3] 00 74 16 A1 08 [3] 8B 0D 0C [3] 03 48 14 89 4D CC }

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 3-5 specific false positive scenarios for the eXPressorv1451CGSoftLabs detection rule, including suggested filters and exclusions:

• Scenario: Scheduled Antivirus Scans on Shared Drives

  • Context: Enterprise Endpoint Protection suites (e.g., Symantec Endpoint Protection, McAfee Total Protection) often perform scheduled deep scans of network shares containing legacy documents or archives. The eXPressor engine may flag the scanning process itself or specific compressed archives within these folders as suspicious due to heuristic matching against known CGSoftLabs signatures.
  • Filter/Exclusion: Create a YARA exclusion rule that ignores alerts originating from processes with ImageName containing Symantec*, McAfee*, or Sophos* when the file path resides within standard shared drive prefixes (e.g., \\FileServer\SharedDocs\).

• Scenario: Deployment of Legacy Reporting Tools via SCCM

  • Context: IT Operations teams frequently deploy legacy reporting utilities using Microsoft System Center Configuration Manager (SCCM) or Intune. These deployments often involve installing .msi packages that include the eXPressor component for data processing. The rule may trigger during the initial installation phase when the installer extracts and executes these components in temporary directories.
  • Filter/Exclusion: Exclude alerts where the ParentProcessName is ccmsetup.exe, wuauserv.exe, or msiexec.exe and the file path contains \AppData\Local\Temp\ or \Windows\Installer\.

• Scenario: Automated Backup Jobs by Veeam or Commvault

  • Context: Data center backup solutions like Veeam Backup & Replication or Commvault utilize internal engines to compress and encrypt data blocks