SecuPackv15

Hunt Hypothesis

This hypothesis targets the presence of the SecuPack v15 packer, a technique often used by adversaries to compress or obfuscate malicious payloads to evade static analysis and signature-based detection. Proactively hunting for this specific packer in Azure Sentinel allows the SOC team to identify potentially hidden or modified executables before they can be executed, reducing the risk of low-severity threats that may serve as initial access vectors or part of a larger attack chain.

YARA Rule

rule SecuPackv15
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 83 C4 F0 53 56 57 33 C0 89 45 F0 B8 CC 3A 40 ?? E8 E0 FC FF FF 33 C0 55 68 EA 3C 40 ?? 64 FF 30 64 89 20 6A ?? 68 80 [3] 6A 03 6A ?? 6A 01 [3] 80 }

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

• Antivirus/EDR Signature Updates: When an endpoint protection agent (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint, or SentinelOne) downloads and applies new signature packs or behavioral rule updates, the binary or configuration file may contain byte patterns that match the SecuPackv15 YARA rule.
  • Filter/Exclusion: Exclude files located in the vendor-specific update directories (e.g., C:\Program Files\CrowdStrike\ or C:\ProgramData\Microsoft Defender\) or filter by process names like FalconSensor.exe, MsMpEng.exe, or SentinelOneAgent.exe performing the write operation.
• Software Distribution via Group Policy or SCCM: When enterprise software (such as Java, .NET Framework, or Adobe Reader) is deployed via Group Policy Software Installation or System Center Configuration Manager (SCCM), the installer or the resulting application binaries may be compressed or packed in a way that triggers the “packed executable” or specific signature match.
  • Filter/Exclusion: Exclude processes associated with the deployment engine, such as wuaexhost.exe (Windows Update), ccmexec.exe (SCCM Client), or gpupdate.exe, or filter by file paths within the C:\Windows\Installer or C:\Program Files\ directories during known maintenance windows.
• Backup and Archiving Agents: Backup solutions like Veeam, Commvault, or Acronis often create temporary snapshot files or compressed archives (e.g., .vbk, .cab, or .zip) that contain packed or compressed data structures. If the YARA rule scans these temporary files or the backup agent’s own binary, it may flag the compressed data as a match.
  • Filter/Exclusion: Exclude processes like VeeamBackup.exe, commvault.exe, or