iexpl0re family

Hunt Hypothesis

The iexpl0re family is associated with low-severity reconnaissance activities that may indicate initial foothold attempts by adversaries. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify potential early-stage threats and prevent further lateral movement.

YARA Rule

rule iexpl0re : Family
{
    meta:
        description = "iexpl0re family"
        author = "Seth Hardy"
        last_modified = "2014-07-21"
   
    condition:
        iexpl0reCode or iexpl0reStrings
        
}

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
• Source Rule

False Positive Guidance

• Scenario: Legitimate scheduled task running Internet Explorer for automated reporting
  Filter/Exclusion: process.parent_process_name != "schtasks.exe" or process.name != "iexplore.exe"

• Scenario: Admin using Internet Explorer to access internal SharePoint site
  Filter/Exclusion: process.parent_process_name != "explorer.exe" or process.command_line contains "sharepoint"

• Scenario: System update using Microsoft Edge to download and install patches
  Filter/Exclusion: process.name != "msedge.exe" or process.command_line contains "update"

• Scenario: User running a legacy application that requires Internet Explorer in compatibility mode
  Filter/Exclusion: process.name != "iexplore.exe" or process.command_line contains "appcmd"

• Scenario: IT staff using Internet Explorer to perform browser compatibility testing
  Filter/Exclusion: process.parent_process_name != "cmd.exe" or process.command_line contains "compatibility testing"