COPv10c1988

Hunt Hypothesis

This hunt hypothesis targets adversary behavior characterized by the execution of specific malicious binaries identified by the COPv10c1988 YARA signature, which often indicates early-stage reconnaissance or lateral movement activities within the network. A SOC team should proactively hunt for this indicator in Azure Sentinel to validate the presence of known threat patterns that may have evaded initial automated detections due to their low severity classification.

YARA Rule

rule COPv10c1988
{
      meta:
		author="malware-lu"
strings:
		$a0 = { BF [2] BE [2] B9 [2] AC 32 [3] AA E2 ?? 8B [3] EB ?? 90 }

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 5 specific false positive scenarios for the COPv10c1988 YARA rule, tailored for a legitimate enterprise environment:

• Scenario: Microsoft Defender Antivirus Scheduled Scans

  • Context: The daily or weekly scheduled full scan initiated by the Windows Task Scheduler triggers the rule because the MsMpEng.exe process loads multiple signature definition modules and scans system directories, matching the YARA pattern for suspicious file enumeration.
  • Filter/Exclusion: Exclude processes where ProcessName equals MsMpEng.exe AND CommandLine contains /scheduledscan. Alternatively, add a whitelist entry for the specific hash of the current Microsoft Defender engine version.

• Scenario: SCCM (Configuration Manager) Software Deployment

  • Context: During a mass deployment of a new application package via System Center Configuration Manager, the ccmsetup.exe or CcmExec.exe agents extract installation archives and write temporary files to %TEMP%, which mimics the behavior detected by COPv10c1988.
  • Filter/Exclusion: Create a detection exclusion for processes running under the user context of NT SERVICE\CCM or filter events where the parent process is ccmsetup.exe.

• Scenario: CrowdStrike Falcon Sensor Real-Time Protection

  • Context: The CrowdStrike Falcon sensor (Cnsys.exe) frequently scans and monitors executable files in real-time, particularly when a user opens a document that triggers an embedded macro or script. This activity often matches the YARA rule’s criteria for file access patterns.
  • Filter/Exclusion: Exclude alerts where ProcessName is Cnsys.exe and the source directory path starts with C:\Program Files\CrowdStrike\Falcon.

• **Scenario: Veeam Backup &