MaskPEV20yzkzero

Hunt Hypothesis

This rule detects the presence of a specific, low-severity YARA signature (MaskPEV20yzkzero) that may indicate a known malware variant or suspicious binary artifact within the environment. Proactively hunting for this signature allows the SOC team to identify potentially dormant or overlooked threats in Azure Sentinel, ensuring that even low-fidelity indicators are investigated to prevent lateral movement or data exfiltration.

YARA Rule

rule MaskPEV20yzkzero
{
      meta:
		author="malware-lu"
strings:
		$a0 = { B8 18 00 00 00 64 8B 18 83 C3 30 C3 40 3E 0F B6 00 C1 E0 ?? 83 C0 ?? 36 01 04 24 C3 }

condition:
		$a0
}

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

• Scenario: A developer or DevOps engineer runs a static analysis tool like radare2 or Ghidra to reverse-engineer a proprietary binary or library, causing the YARA rule to match the in-memory or on-disk representation of the PE header structures.
  • Filter/Exclusion: Exclude processes where the parent process is radare2.exe, ghidra_run.bat, or ida64.exe, or where the file path contains \tools\bin\ or \dev\.
• Scenario: An IT administrator performs a routine backup or snapshot of a virtual machine using Veeam Backup & Replication or Windows Server Backup, which temporarily creates a raw disk image or memory dump that matches the YARA signature for the PE structure.
  • Filter/Exclusion: Exclude alerts where the file extension is .vbk, .vib, or .bak, or where the process name is vbrsrvr.exe or wbadmin.exe.
• Scenario: A security team runs a memory forensic tool like Volatility3 or Rekall to analyze a captured memory dump (*.dmp or *.raw), which parses PE headers and may trigger the rule if the tool’s own binary or the analyzed artifact matches the mask.
  • Filter/Exclusion: Exclude processes named vol3.exe, rekall.exe, or memdump.exe, and exclude file paths ending in .dmp, .raw, or .mem.
• Scenario: A CI/CD pipeline (e.g., Jenkins or GitLab CI) compiles a C/C++ project and generates a .exe or .dll artifact that is temporarily stored in a workspace directory before being scanned, triggering the rule on the newly built binary.
  • Filter/Exclusion: Exclude