HACKSTOPv118

Hunt Hypothesis

This YARA rule targets specific memory patterns or code artifacts associated with the HACKSTOPv118 signature, potentially indicating the presence of a known malware strain or a custom implant in process memory. Proactively hunting for this signature in Azure Sentinel allows the SOC to identify low-severity intrusions or persistent threats that may evade standard behavioral detections, ensuring early containment of targeted or stealthy adversary activity.

YARA Rule

rule HACKSTOPv118
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 52 BA [2] 5A EB ?? 9A [4] 30 CD 21 [3] FD 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 DevOps engineer runs a local build script using make or cmake that compiles a C/C++ project containing specific string literals or byte patterns matching the HACKSTOPv118 signature (e.g., hardcoded API keys, debug strings, or specific library headers) on a build server or developer workstation.

  • Filter/Exclusion: Exclude processes where the parent process is make.exe, cmake.exe, ninja.exe, or msbuild.exe, or restrict the rule to exclude file paths under standard build directories like C:\builds\, /var/lib/builds/, or D:\projects\.

• Scenario: An IT administrator uses a legitimate network scanning or vulnerability assessment tool (such as Nmap, Masscan, or OpenVAS) that spawns child processes or writes temporary files containing data packets or configuration snippets that inadvertently match the YARA pattern due to embedded protocol headers or test payloads.

  • Filter/Exclusion: Exclude processes initiated by known scanning tools like nmap.exe, masscan.exe, or openvas-scanner, or filter out events where the source IP is within the designated network operations subnet (e.g., 10.20.0.0/24).

• Scenario: A scheduled maintenance job runs a database backup or log rotation script (e.g., pg_dump, mysqldump, or a custom PowerShell script) that writes large binary or text files to disk, where the content includes specific magic bytes or repeated string sequences (e.g., “HACKSTOP”, “DEBUG”, or specific version strings) that trigger the YARA match.

  • Filter/Exclusion: Exclude file creation events where the parent process is pg_dump.exe, mysqldump.exe, or powershell.exe with