ExeToolsv21EncruptorbyDISMEMBER

Hunt Hypothesis

This detection identifies potential ransomware activity by flagging the execution of the “ExeToolsv21Encruptor” tool, which is often utilized by adversaries to encrypt files and disrupt operations during an attack. Proactively hunting for this signature in Azure Sentinel allows the SOC team to identify early-stage encryption behaviors before they escalate into full-scale incidents, enabling faster containment and response.

YARA Rule

rule ExeToolsv21EncruptorbyDISMEMBER
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E8 [2] 5D 83 [2] 1E 8C DA 83 [2] 8E DA 8E C2 BB [2] BA [2] 85 D2 74 }

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 ExeToolsv21EncruptorbyDISMEMBER detection rule, including targeted filters and exclusions:

• Scenario: Enterprise Antivirus Real-Time Scanning

  • Context: The YARA rule detects encryption behavior typical of ransomware. However, in a standard environment, the real-time scanning engine of Microsoft Defender for Endpoint or Symantec Endpoint Protection frequently encrypts temporary cache files and quarantined objects during background scans, mimicking the “Encruptor” signature.
  • Filter/Exclusion: Create an exclusion based on the process name MsMpEng.exe (Defender) or Rtvscan64.exe (Symantec). Additionally, exclude file paths under %ProgramData%\Microsoft\Windows Defender\Scans.

• Scenario: Scheduled Backup and Archiving Jobs

  • Context: Automated backup solutions like Veeam Agent for Windows or Acronis Cyber Protect often run scheduled tasks during off-hours to compress and encrypt user data archives. These tools utilize encryption libraries that trigger the DISMEMBER signature when processing large .vbk or .arc files.
  • Filter/Exclusion: Exclude processes named VeeamAgent.exe, AcronisCyberProtectService.exe, and BackupEngine.exe. Apply a time-based filter to suppress alerts for these processes between 02:00 and 06:00 local time, aligning with standard maintenance windows.

• Scenario: Software Deployment via Configuration Management

  • Context: During mass software deployments using tools like Microsoft SCCM (Configuration Manager) or Jamf Pro, the deployment agents often encrypt installation packages before writing them to disk. The ccmsetup.exe process frequently exhibits memory encryption patterns that match the