HACKSTOPv111c

Hunt Hypothesis

This YARA rule targets specific memory patterns or code artifacts associated with the HACKSTOPv111c signature, potentially indicating the presence of a known malware family or exploit kit component within Azure workloads. Proactively hunting for this indicator allows the SOC to identify low-severity, stealthy intrusions that may be evading traditional network-based detections before they escalate to lateral movement or data exfiltration.

YARA Rule

rule HACKSTOPv111c
{
      meta:
		author="malware-lu"
strings:
		$a0 = { B4 30 CD 21 86 E0 3D [2] 73 ?? B4 ?? CD 21 B0 ?? B4 4C CD 21 53 BB [2] 5B 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 uses Wireshark or tcpdump on a jump host to capture network traffic for troubleshooting latency issues. The YARA rule HACKSTOPv111c likely scans memory or disk for specific byte patterns associated with network sniffing tools or their compiled binaries, triggering a match on the executable or its loaded libraries.

  • Filter/Exclusion: Exclude processes where the parent process is wireshark.exe, tshark.exe, or tcpdump.exe, or exclude files located in standard tool directories like C:\Program Files\Wireshark\ or /usr/bin/.

• Scenario: An IT administrator runs Process Explorer (Sysinternals) or Process Monitor to diagnose a hung service or high CPU usage on a Windows server. These tools often load specific DLLs or maintain memory structures that match the byte signatures defined in HACKSTOPv111c, which may be targeting common debugging or inspection toolkits.

  • Filter/Exclusion: Exclude processes named procexp.exe, procmon.exe, or procexp64.exe, and restrict the detection to non-system drives (e.g., exclude C:\Sysinternals\ or C:\Tools\).

• Scenario: A scheduled maintenance job runs 7-Zip (7z.exe) to compress and archive log files for offsite backup. If the YARA rule is designed to detect specific compression algorithms or archive headers that overlap with known hacktool signatures, the legitimate archive utility may trigger a false positive during the compression process.

  • Filter/Exclusion: Exclude processes named 7z.exe, 7za.exe, or 7zG.exe, and exclude paths containing \Archive\, \Backup\, or \Logs\ where compression tools are commonly stored.