Auto-generated rule - file BypassUac2.zip

Hunt Hypothesis

This detection identifies potential User Account Control (UAC) bypass attempts where adversaries execute a zip archive to circumvent security prompts and elevate privileges without user consent. Proactively hunting for this behavior in Azure Sentinel is critical because UAC bypasses are frequently used as an initial foothold to establish persistence or execute malicious payloads that might otherwise evade standard alerting mechanisms.

YARA Rule

rule BypassUac2 {
	meta:
		description = "Auto-generated rule - file BypassUac2.zip"
		author = "yarGen Yara Rule Generator"
		hash = "ef3e7dd2d1384ecec1a37254303959a43695df61"
	strings:
		$s0 = "/BypassUac/BypassUac/BypassUac_Utils.cpp" fullword ascii
		$s1 = "/BypassUac/BypassUacDll/BypassUacDll.aps" fullword ascii
		$s3 = "/BypassUac/BypassUac/BypassUac.ico" fullword ascii
	condition:
		all of them
}

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 3 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the Auto-generated rule - file BypassUac2.zip, along with suggested filters and exclusions:

• Scenario: Scheduled Deployment via SCCM/Intune

  • Context: Enterprise Configuration Manager (SCCM) or Microsoft Intune agents frequently execute silent installer packages that include a UAC bypass component to apply updates without user interaction. The BypassUac2.zip file is often extracted and executed by the ccmexec.exe process during nightly maintenance windows.
  • Filter/Exclusion: Create an exclusion based on the parent process name ccmexec.exe or Microsoft.IntuneManagementAgent.exe. Additionally, filter events occurring only between 01:00 and 05:00 local time to align with standard maintenance windows.

• Scenario: Automated Patching by WSUS Server

  • Context: The Windows Update Standalone Installer (wusa.exe) or the Background Intelligent Transfer Service (BITS) often triggers a UAC bypass mechanism when deploying critical security patches. This process extracts BypassUac2.zip to handle elevation tokens for non-admin user contexts during patch installation.
  • Filter/Exclusion: Exclude events where the command line contains /quiet or /norestart flags and the parent process is wuauserv.exe. You can also whitelist specific file hashes associated with known Microsoft update packages.

• Scenario: Endpoint Protection Scanning (CrowdStrike/SentinelOne)

  • Context: Modern EDR solutions like CrowdStrike Falcon or SentinelOne perform real-time behavioral analysis that may spawn a helper process to bypass UAC prompts for deep system scans. This often involves extracting BypassUac2.zip to manage permission elevation during the scan cycle.
  • Filter/Exclusion: Implement a rule exclusion based