WinZip32bitSFXv6xmodule

Hunt Hypothesis

This rule identifies the presence of WinZip 32-bit self-extracting archive (SFX) modules, which adversaries frequently use to package and deliver malicious payloads while evading initial static analysis. Proactively hunting for these artifacts allows the SOC team to uncover hidden executable components that may have been dropped during lateral movement or initial access, ensuring that low-severity but potentially critical staging files are not overlooked in the Azure Sentinel environment.

YARA Rule

rule WinZip32bitSFXv6xmodule
{
      meta:
		author="malware-lu"
strings:
		$a0 = { FF 15 [3] 00 B1 22 38 08 74 02 B1 20 40 80 38 00 74 10 38 08 74 06 40 80 38 00 75 F6 80 38 00 74 01 40 33 C9 [4] FF 15 }

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

• Legacy Application Installer Execution: An IT administrator runs a self-extracting archive (SFX) created with WinZip 6.x to install a legacy 32-bit line-of-business application (e.g., an older version of a specific ERP client or CAD tool) on a domain-joined workstation.

  • Filter/Exclusion: Exclude files located in standard installation directories (e.g., C:\Program Files (x86)\[AppName]\) or exclude processes initiated by known service accounts (DOMAIN\svc-installer) where the parent process is explorer.exe or cmd.exe and the file extension is .exe or .zip.

• Software Distribution via SCCM/Intune: The System Center Configuration Manager (SCCM) or Microsoft Intune agent deploys a software package that contains a WinZip SFX wrapper to handle dependency installation or pre-install scripts. The SFX executable is dropped into the temporary deployment folder (e.g., C:\Windows\CCM\ or C:\ProgramData\Intune\) and executed by the ccmexec.exe or msiexec.exe process.

  • Filter/Exclusion: Exclude paths under C:\Windows\CCM\, C:\ProgramData\Intune\, or C:\Windows\Installer\ where the parent process is ccmexec.exe, msiexec.exe, or agentd.exe.

• Vendor-Specific Support Tool Deployment: A vendor support engineer (e.g., from a firewall or database vendor) runs a diagnostic or patch tool distributed as a WinZip SFX archive. The tool is executed from a user’s Downloads folder or a specific vendor tool directory (e.g., C:\Tools\[VendorName]\) by a user with elevated privileges, often triggered by a double-click or a scheduled task created for the session.