Pohernah102byKas

Hunt Hypothesis

This detection identifies potential malicious file execution or persistence activities captured by the “Pohernah102byKas” YARA signature, which may indicate early-stage adversary reconnaissance or tool deployment within the environment. Proactive hunting for this signal in Azure Sentinel is essential to uncover low-severity indicators that could represent initial footholds before they escalate into more severe incidents.

YARA Rule

rule Pohernah102byKas
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 E8 00 00 00 00 5D 81 ED DE 26 40 00 8B BD 05 28 40 00 8B 8D 0D 28 40 00 B8 25 28 40 00 01 E8 80 30 05 83 F9 00 74 71 81 7F 1C AB 00 00 00 75 62 8B 57 0C 03 95 09 28 40 00 31 C0 51 31 C9 66 B9 F7 00 66 83 F9 00 74 49 8B 57 0C 03 95 09 28 40 00 8B 85 11 28 40 00 83 F8 02 75 06 81 C2 00 02 00 00 51 8B 4F 10 83 F8 02 75 06 81 E9 00 02 00 00 57 BF C8 00 00 00 89 CE E8 27 00 00 00 89 C1 5F B8 25 28 40 00 01 E8 E8 24 00 00 00 59 49 EB B1 59 83 C7 28 49 EB 8A 8B 85 01 28 40 00 89 44 24 1C 61 FF E0 56 57 4F F7 D7 21 FE 89 F0 5F 5E C3 60 83 F0 05 40 90 48 83 F0 05 89 C6 89 D7 60 E8 0B 00 00 00 61 83 C7 08 83 E9 07 E2 F1 61 C3 57 8B 1F 8B 4F 04 68 B9 79 37 9E 5A 42 89 D0 48 C1 E0 05 BF 20 00 00 00 4A 89 DD C1 E5 04 29 E9 8B 6E 08 31 DD 29 E9 89 DD C1 ED 05 31 C5 29 E9 2B 4E 0C 89 CD C1 E5 04 29 EB 8B 2E 31 CD 29 EB 89 CD C1 ED 05 31 C5 29 EB 2B 5E 04 29 D0 4F 75 C8 5F 89 1F 89 4F 04 C3 }

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

Here are 4 specific false positive scenarios for the Pohernah102byKas YARA rule, including suggested filters and exclusions tailored for a legitimate enterprise environment:

• Scenario: Automated Endpoint Protection Scans

  • Context: Scheduled antivirus or EDR agents (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint) performing full system scans often trigger file integrity checks that match the YARA signature’s heuristics regarding file modification patterns.
  • Filter/Exclusion: Create a process exclusion for known security daemons.
    • Action: Exclude processes named C:\Program Files\CrowdStrike\fs_qc.exe and C:\Windows\System32\mpcmdrun.exe from this rule’s scope, or add a condition to ignore events where the parent process is a recognized security vendor executable.

• Scenario: Software Deployment via Configuration Management

  • Context: Automated deployment tools like Microsoft SCCM (Configuration Manager), Ansible, or Chocolatey push updates and install patches during maintenance windows. These tools frequently write configuration files or scripts that mimic the behavioral patterns detected by the rule.
  • Filter/Exclusion: Whitelist specific service accounts used for deployments.
    • Action: Exclude events generated by the NT SERVICE\CCMExec (SCCM) and NT SERVICE\ChocolateyInstall service accounts, or filter out file paths located within standard deployment directories such as C:\Windows\CCMCache\.

• Scenario: Scheduled PowerShell Maintenance Scripts

  • Context: IT operations teams often run scheduled tasks (via Windows Task Scheduler) that execute complex PowerShell scripts to clean logs, rotate archives, or update inventory databases. These scripts frequently invoke the .NET runtime and modify files in ways that trigger the rule’s logic.
  • **Filter/Ex