DualseXeEncryptor10bDual

Hunt Hypothesis

This hunt targets adversary behavior involving the execution of dual-stage encryption processes characteristic of ransomware families like Dualse, which often employ multi-phase file locking to evade initial detection. Proactive hunting for this specific YARA signature in Azure Sentinel is essential to identify early-stage encryption activities before they escalate into widespread data unavailability and operational disruption.

YARA Rule

rule DualseXeEncryptor10bDual
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 81 EC 00 05 00 00 E8 00 00 00 00 5D 81 ED 0E 00 00 00 8D 85 3A 04 00 00 89 28 33 FF 8D 85 80 03 00 00 8D 8D 3A 04 00 00 2B C8 8B 9D 8A 04 00 00 E8 24 02 00 00 8D 9D 58 03 00 00 8D B5 7F 03 00 00 46 80 3E 00 74 24 56 FF 95 58 05 00 00 46 80 3E 00 75 FA 46 80 3E 00 74 E7 50 56 50 FF 95 5C 05 00 00 89 03 58 83 C3 04 EB E3 8D 85 69 02 00 00 FF D0 8D 85 56 04 00 00 50 68 1F 00 02 00 6A 00 8D 85 7A 04 00 00 50 }

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 DualseXeEncryptor10bDual detection rule, including suggested filters and exclusions:

• Antivirus Real-Time Scanning of Large Archives

  • Scenario: When enterprise endpoint protection suites (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint, or Symantec Endpoint Protection) perform real-time scanning on large .7z or .zip archives containing mixed file types, the heuristic engine often triggers the “Dual Encryption” signature due to nested compression and encryption layers.
  • Suggested Filter/Exclusion: Create a process exclusion for the AV service executables (e.g., C:\Program Files\CrowdStrike\fsfalcon.exe or MsMpEng.exe) when the parent process is the antivirus engine itself, specifically targeting file paths ending in .zip, .7z, or .rar.

• Scheduled Backup Jobs with Encrypted Volumes

  • Scenario: Automated backup solutions like Veeam Backup & Replication, Commvault, or Rubrik frequently encrypt data streams during nightly scheduled jobs. The rule may flag the backup agent’s interaction with encrypted volume mounts (e.g., BitLocker-protected drives) as a potential dual-encryption event.
  • Suggested Filter/Exclusion: Exclude processes running under specific service accounts (e.g., DOMAIN\VeeamService or SYSTEM) during known maintenance windows (e.g., 01:00–05:00 local time) where the destination path matches backup repository directories (e.g., D:\VeeamBackup\).

• Software Deployment via Configuration Management Tools

  • Scenario: During software deployment cycles, tools like Microsoft SCCM (ConfigMgr), Ansible, or Chocolatey often install applications