HACKSTOPv119

Hunt Hypothesis

This YARA rule targets specific memory patterns or code artifacts associated with the HACKSTOPv119 signature, potentially indicating the presence of a known malware strain or a custom implant in process memory. Proactively hunting for this signature allows the SOC to identify low-severity threats that may be evading traditional network-based detections, ensuring early containment of persistent or stealthy adversary footholds within the Azure environment.

YARA Rule

rule HACKSTOPv119
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 52 BA [2] 5A EB ?? 9A [4] 30 CD 21 [3] D6 02 [2] CD 20 0E 1F 52 BA [2] 5A EB }

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

• Scenario: A developer or sysadmin uses a legitimate binary analysis tool like Ghidra or IDA Pro to reverse-engineer a custom internal application or debug a crash dump. These tools often embed specific string markers or structural patterns that YARA rules targeting “hack tools” or specific C2 frameworks may inadvertently match.
  • Filter/Exclusion: Exclude processes where the parent process is ghidra.exe, idag.exe, or idaw.exe, or exclude file paths containing \ghidra\ or \IDA\.
• Scenario: An automated backup or snapshot job using Veeam Backup & Replication or Commvault creates temporary shadow copies or restore points on a file server. If the rule targets specific file headers or magic bytes associated with encrypted or compressed archives, it may flag these temporary .vbk or .cbt files as suspicious artifacts.
  • Filter/Exclusion: Exclude file extensions .vbk, .cbt, or .cbt2, and exclude processes named VeeamBackup.exe or commvault_agent.exe when accessing these files.
• Scenario: A CI/CD pipeline running Jenkins or GitLab CI executes a build step that compiles a C/C++ project using MinGW or MSYS2. The resulting executable or intermediate object files may contain linker strings or section names that match generic “hacktool” signatures, especially if the build uses non-standard compilers or custom linkers.
  • Filter/Exclusion: Exclude processes named gcc.exe, g++.exe, clang.exe, or link.exe running from directories like C:\msys64\ or C:\MinGW\, and exclude file paths containing \workspace\ or \builds\.
• Scenario: A security