VxKBDflags1024

Hunt Hypothesis

This detection identifies potential keyboard hooking or input monitoring behaviors by analyzing specific virtualized keyboard flag anomalies that often indicate early-stage reconnaissance or credential harvesting activities. A SOC team should proactively hunt for these signals in Azure Sentinel to uncover stealthy adversaries who manipulate user input streams before triggering more obvious authentication events, thereby reducing the dwell time of undetected threats.

YARA Rule

rule VxKBDflags1024
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 8B EC 2E 89 2E 24 03 BC 00 04 8C D5 2E 89 2E 22 }

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 5 specific false positive scenarios for the VxKBDflags1024 detection rule, along with suggested filters and exclusions:

• Scenario: Automated Keyboard Input Simulation by RPA Tools

  • Context: Robotic Process Automation (RPA) tools like UiPath, Automation Anywhere, or Power Automate Desktop frequently simulate keyboard events to interact with legacy applications. These tools often set specific KBD_FLAGS values that mimic the pattern detected by VxKBDflags1024 during high-volume data entry tasks.
  • Filter/Exclusion: Create a process exclusion for known RPA executables (e.g., UiPath.Studio.exe, AutomationAnywhere.Agent.exe) or filter alerts where the parent process is one of these tools and the event occurs within a defined “RPA Execution” time window.

• Scenario: Scheduled Accessibility Feature Activation

  • Context: Enterprise environments often enforce scheduled jobs to enable accessibility features (such as Sticky Keys, Filter Keys, or On-Screen Keyboard) for remote users via Group Policy or Microsoft Endpoint Configuration Manager. When these policies trigger at specific intervals (e.g., 8:00 AM daily), they modify keyboard flags that match the rule’s signature.
  • Filter/Exclusion: Exclude alerts generated by the svchost.exe process when the parent is gpsvc (Group Policy Client) or ccmexec.exe, specifically during the scheduled maintenance window defined in the enterprise policy schedule.

• Scenario: Macro Execution in Microsoft Office Suite

  • Context: Users running complex VBA macros in Microsoft Excel or Word often utilize keyboard input simulation to populate forms or trigger workflows. The macro engine modifies low-level keyboard flags, which can be misinterpreted as the specific KBD_FLAGS anomaly targeted